Words are defined by consensus of the community using them. That's the primary source of semantic meaning.
Next one down is dictionary definition (or claim to authority, for example a tweet where the term was first used). But community meaning takes precedence.
Authors are free to use a nonstandard meaning but should provide readers with their definition if they want to be understood.
> Words are defined by consensus of the community using them.
No. That would make it impossible for someone new to a community to communicate with a community, all while at the same time a community isn't going to accept someone new who isn't communicating. Yet clearly people do join communities.
What happens in reality is that everyone accepts that the speaker's definition reigns supreme, and if there is suspicion – absent of a definition – that there is a discrepancy between the speaker's definition and own's own definition, the speaker will be asked to clarify.
A speaker may eventually adopt a community's definition, but that doesn't always happen either. Look at the Rust users here. They hang desperately onto words like enum that do not match the community definition. But it doesn't really matter, does it? We remember that when they say enums they really mean sum types and move on with life.
1. All speakers of a language
2. Speakers in a region (dialect)
3. Subgroups like teenagers, engineers, gamers, redditors
4. Sub-sub groups like teenagers from a specific school, engineers of a specific discipline, gamers of a certain game
x. Personal dialect (idiolect), which is a sub group that exists separately to all of these and is most closely related to family and the friend group you had as a child and teenager.
We are all members of many different groups which intermesh, and we seemlessly switch meaning and pronunciation as we do that (code switching).
When joining a community, people start at the top (learn French) then move through subgroups. Dictionaries and textbooks are designed to match as closely as possible to the top level community's consensus of word meaning, which, being large, is also the most static. But any language learner will know that textbooks can only get you so far in learning how language is actually spoken day to day. You have to join the community to learn that.
The same applies as you go down to dialects and other sub groups. You can learn a bit before you join, but becoming a part of the community, linguistically, can only happen after joining.
Next one down is dictionary definition (or claim to authority, for example a tweet where the term was first used). But community meaning takes precedence.
Authors are free to use a nonstandard meaning but should provide readers with their definition if they want to be understood.