Equivocation

In the strictest sense, equivocation is the use of different senses of a word as if they were the same thing; see Wikipedia:Equivocation for more on this usage.

In a broader sense, equivocation need not be limited to a single word; a phrase or even concept may have different facets or be applied to different instances of the same idea which, although related, are not freely interchangeable:

• Person A: I refuse to continue this argument without a mediator.
• Person B: No, I won't allow you to just back out of this. You don't have the right.
• Person A: I don't need your approval; those are my terms, take them or leave them.
• Person B: So what's to negotiate? You've already dictated your terms.

In this case, Person B is equivocating Person A's usage of "terms", meaning terms under which A is willing to continue discussing the matter, with "terms" which might be arrived at in discussion of those matters (presumably with a mediator). (In the real-world example from which this was excerpted and paraphrased, there was substantial discussion between the last two lines, making it less obvious where the equivocation had taken place.)

Notes

This might also be called "Confusion of Terms", though I have not been able to find any references to that phrase clearly used in this way.