Appeal to definition

So the fallacy here is using a dictionary’s limited definition of a term as evidence that term cannot have another meaning, expanded meaning, or even conflicting meaning. So for example, this would NOT be a fallacy:

Person 1: I may be stupid, but I am no moron.
Person 2: Actually, the definition of "moron" is "a stupid person".

This is where the fallacy comes in:

Person 1: When I accused you of acting like a moron, I meant that you acted foolishly, I didn't mean that you were stupid.
Person 2: The definition of "moron" is "a stupid person", so you did mean that I was stupid.