mistake for(redirected from mix up with)
mistake (someone) for (someone else)and mix (someone) up with (someone else)
to confuse someone with someone else; to think that one person is another person. I'm sorry. I mistook you for John. Tom is always mistaking Bill for me. We don't look a thing alike, though. Try not to mix Bill up with Bob, his twin.
mistake (something) for (something else)and mix (something) up with (something else)
to confuse two things with each other. Please don't mix this idea up with that one. I mistook my book for yours.
Take someone or something for someone or something else, as in I'm sorry, I mistook you for her sister, or Don't mistake that friendly smile for good intentions; he's a tough competitor. [c. 1600]
To wrongly perceive that someone or something is someone or something else: I'm sorry to have bothered you—I mistook you for a friend of mine. Don't mistake the poison ivy for a box elder vine!