A guarded definition is one where at least one position suspects there will be pressure to stretch a concept and make it cover more than it ought to, and so they set aside a term meant to refer narrowly to the things inside the concept. Thus, if a term has been designated as a ‘guarded definition’, stretching it to cover new and non-central members that are not very clearly part of the definition, and agreed to be so by those who wanted to designate it as guarded, is an unusually strong discourtesy. If the term was originated (or its special meaning was originated) specifically in order to set it aside as a narrow and guarded term, then it is a discourse norm to respect that narrow meaning and not try to extend it.
Example: Suppose that Alice and Bob are having a conversation about natural selection. Alice points out that since everything occurs within Nature, all selection, including human agricultural breeding and genetic engineering, seems to her like ‘natural selection’, and she also argues that consumer choice in supermarkets is an instance of ‘natural selection’ since people are natural objects and they’re selecting which foods to buy, and thus her paper on watching people buy food in supermarkets ought to be funded by a program on evolutionary biology. If Bob and his researchers then begin using the term ‘ecologically natural selection’ because they think it’s important to have a narrow term to refer to just birds breeding in the wild and not consumer choice in supermarkets, it is an extreme discourtesy (and a violation of what we locally take to be discourse norms) for Alice to start arguing that really supermarkets are instances of ecologically natural selection too.
What is truth?