opposite number, one's
One's counterpart, as in He's my opposite number in the California office. This expression is generally used for a person's equivalent in another organization or system (number alluding to their position in a hierarchy). [c. 1900]
These Common Words Have Some Very Uncommon OppositesYou know up is the opposite of down, but do you know the antonyms of ambidextrous and placebo? English isn't always black and white.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.