New definitions that are added to a language as that language grows are called

I believe the answer is: stipulative

A stipulative would not exist in the standard dictionary of the language but often necessary for understanding sentence or discussion in a given context.
For example, before the creation of the company the word 'google' does not have any meaning. But now, you would notice that most people use the word 'google' as a verb to define the act of searching for information on the internet.