There are two ideas which cause trouble when thinking about definitions, and what a good definition may look like.
- The first toxic idea is that you can produce a definition which explains all meanings of a term, for everyone, anytime, and everywhere. It is the idea that you can make a successful universal definition.
- The second toxic idea, strongly related to the first, is that you can restrict, via the definition, the conclusions which anyone can draw from it. If you think that meaning aggregates all conclusions that you can derive knowing the definition, then this second idea is really a facet of the first.
Instead, consider if a definition, or its possible consequences matter to anyone, anytime, everywhere? Probably not.
When was the last time you needed to reason from a definition of ”giraffe”? And if you did, what was the stake with that reasoning? Did it matter if you drew different conclusions from the nearest zoologist? This obviously does not apply to all terms, all the time, and everywhere. It is, for example, of significant importance, that customs officials in all countries agree on the definition of ”passport”, as disagreements there will matter to many, frequently, and in many places. But even then, not everyone has something at stake, all the time.
The point is that the quality of a definition matters at any time only to some, and that they may identify themselves, if doing so can be done at some reasonable cost.
This is where crowds come into play. Wikipedia is an example of a technology which creates term or topic-specific communities (whereby ”topic” I mean somehow related sets of terms). It lowers the cost for people who care enough about the quality of definitions of ”soccer”, to debate, update, and extend the definition of that term. It allows anyone in the crowd, so to speak, to come forward and add or remove to a definition of a term, whose meaning they want to say something about. What matters here is not that the term is defined for universal agreement, or fitness to empirical evidence, but for acceptance by the community of those who worry about the phrasing, content, and consequences or implications of the term being defined in some or other way.
And this is important for innovation, because the team doing innovation is exactly the group most concerned with the meaning of the terms they use to describe their inventions.
With this in mind, a definition is good, or its quality matters only for and within a community – it is its community which promotes desirable, and sanctions undesirable consequences, and judges if it satisfies eliminability or conservativeness. That community, like in many areas of scientific research, may agree on highly specific rules and procedures for producing and validating evidence for something to be in a definition.
The extent to which different communities produce definitions of different quality, can be illustrated by looking at the definition of something recent, with strong emotional content. How about Pikachu?
Editors at the Oxford English Dictionaries (OED) are apparently not the community to ask about this. Sadly, OED has a definition of Pokémon, but not of Pikachu.
”A series of Japanese video games and related media such as trading cards and television programs, featuring cartoon monsters that are captured by players and trained to battle each other.” 
Editors of the Pikachu page on Wikipedia are a slightly more interested group.
”Pikachu are a species of Pokémon, fictional creatures that appear in an assortment of video games, animated television shows and movies, trading card games, and comic books licensed by The Pokémon Company, a Japanese corporation. They are yellow rodent-like creatures with powerful electrical abilities. In most vocalized appearances, including the anime and certain video games, they are primarily voiced by Ikue Otani.” 
But it all pales in comparison with the community at Bulbapedia, an encyclopedia dedicated to Pokémon. This is merely the outline of the entry on Pikachu, a text of more than 15,000 words.
”Pikachu is an Electric-type Pokémon introduced in Generation I. It evolves from Pichu when leveled up with high friendship and evolves into Raichu when exposed to a Thunder Stone. However, the starter Pikachu in Pokémon Yellow will refuse to evolve into Raichu unless it is traded and evolved on another save file. In Alola, Pikachu will evolve into Alolan Raichu when exposed to a Thunder Stone. Pikachu is popularly known as the mascot of the Pokémon franchise and a major representative of Nintendo’s collective mascots. It is also the game mascot and starter Pokémon of Pokémon Yellow and Pokémon: Let’s Go, Pikachu!. It has made numerous appearances on the boxes of spin-off titles. Pikachu is also the starter Pokémon in Pokémon Rumble Blast and Pokémon Rumble World.” 
Pikachu is an example of an innovation, or part of an innovation (if you take Pokémon to be the innovation). It is one of many terms used when talking, or in general communicating about Pokémon.
Pikachu is an interesting example, because it is an abstraction which becomes somewhat more concrete in cartoons, video games, and any other place it appears, in drawn or other format. There is no thing, object, in nature, which was named Pikachu, and so, there are some properties it has, and which anyone who has access to that object can ascertain. There are properties its authors, designers, chose to represent. But as the community formed around it, the definition will be a reflection of what they see in it. Is there a unique, universal, objective, or otherwise observer-independent canonical definition of Pikachu? No, and thus we fall back on the interested crowd to tell us what they think about the definition of Pikachu, given the concretizations of Pikachu, the imagination of each member of this crowd, and the persistence of each one of them to promote and defend their own idea of Pikachu.
Now, replace ”Pikachu” above, with the term ”nuclear weapon”, or ”agricultural subsidy”, and the important point remains, that there is an interested community, which decides the definition. Evidently, the effects of these choices, their gravity, is clearly different for ”Pikachu” and ”nuclear weapon”.
To see the second important point, consider this question: What do we get by having a community agree on one definition of Pikachu? If differences of opinion on the definition of Pikachu have no bearing on the actions of those who are concerned with that definition, then there is no reason to ever worry about this. In any other case, it is a question of how much their actions matter, and how divergence in opinion, on the definition, affects their actions. So for nuclear weapons, agreement on the definition is critical, since it influences defence policies, and through them, the lives of many, including most directly those in defense industries, in various countries.
The second important point is that agreement on a definition influences coordination, that is, by influencing individual actions of those who agreed, it influences how they act together, and thus the outcomes of their joint actions.
The third important point is that the definition lives and dies with its community. As that community changes – which simply means as it gets new members, loses others, and as they change their minds – so will the definition. For some terms, especially if they refer to things whose properties can be ascertained through repeatable procedures that yield consistent outcomes, these changes may be mild over long periods of time (e.g., ”electricity”, ”magnetic field”, ”atom”, etc.), while they will be more turbulent for others. (Terms used in relation to controversial issues, for example, offer many examples of changing definitions, driven by crowds. Classical such terms include, e.g., ”socialism”, ”atheism”, ”terrorism”, and so on, with ”Napster” and ”The Pirate Bay” being some of many more recent ones.[4,5].)
The fourth important point concerns what a definition looks like. If you are used to printed dictionaries, then the definition looks like a sentence, or a few paragraphs at most, explaining the meaning of a term. Digital resources, however, especially for topics which draw an active community, look nothing like this. They are assemblies of various, more or less structured data, on the term being defined. This is important, because it takes us away from the simplistic one or two sentence definitions, into recognizing that there may be a lot to say about the term, to explain its intended use.
Plastic Definitions are made and changed by a community; early in the innovation process, that community numbers only the team tasked with that process, and grows if and as the innovation process becomes successful. At any time, a Plastic Definition will be a reflection of a temporary consensus on how to read a term, and from there – and more importantly – on what to do about it. It should be precise, clear, and accurate, so as to help others be, in turn, precise, clear, and accurate about what they agree or disagree with, and stimulate them to act to make changes. Finally, a Plastic Definition is how the community explains the term. If it satisfies some weak form of eliminability and conservativeness, it does so only to the extent that this does not hinder it being precise, accurate, and clear for those in the community.
- Pokémon | Definition of Pokémon in English by Oxford Dictionaries. 2019. url: http://en.oxforddictionaries.com/definition/pokemon
- Wikipedia – Pikachu. 2019. url: https://en.wikipedia.org/wiki/Pikachu
- Bulbapedia – Pikachu. 2019. url: https://bulbapedia.bulbagarden.net/wiki/Pikachu
- Wikipedia – List of Controversial Issues. 2019. url: http://en.wikipedia.org/wiki/Wikipedia:List_of_controversial_issues
- Taha Yasseri et al. “The Most Controversial Topics in Wikipedia”. In: Global Wikipedia: International and cross-cultural issues in online collaboration 25 (2014).