Wiktionary
n. (context idiomatic English) A person who holds a position in an organization that corresponds to that held by another person in an other organization; a counterpart
WordNet
n. a person or thing having the same function or characteristics as another [syn: counterpart, vis-a-vis]
Usage examples of "opposite number".
And for Harry, because of the role he had been obliged to play, most of that dark fury and desire for revenge had been focused on his opposite number in the field, the Spider.
Dmitri and Kiernan's opposite number, Wang, had taken over from Maybury and had set up a tripod of garden tools to hold the drip bag.
A tall vase of flowers had been idiotically placed upon the table after the fashion of restaurants, so that no one could see his or her opposite number without cricking his neck.
But at least it wasn't permanently on view, which was more than you could say for its opposite number.
The miners were not supposed to do sentry duty, but their officer had struck a deal with his opposite number in the infantry.
It was almost full size now, and given that it was the littlest finger anyway, it looked full grown unless she held it against its opposite number.