1. To copulate so as to produce children or offspring with. The female praying mantis is notorious for eating the head of its male mate after—or sometimes while—mating with him. A: "She's a nice girl and all, but I don't know if she's someone I'd want to mate with." B: "Ugh, can you please not refer to it as 'mating'?"
2. To pair an animal with a mate so that the two will copulate and produce offspring. In this usage, a noun or pronoun is used between "mate" and "with." I'm been mating my English bulldog with a number of female dogs around the state.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
mate someone with someoneand mate an animal with some other animal
to pair or breed people or animals. The king sought to mate his daughter with the son of a magician. Harry wanted to mate his guppies with June's guppies.
mate with someone
to marry with someone, and presumably, to copulate with someone. Did you meet anyone you would like to mate with and spend the rest of your life with?
mate with an animal
[for an animal] to copulate with its own kind. The gander mated with the goose in the barnyard. The coyote acted as if it wanted to mate with the dog.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.