matematemates1noun1(British, informal) a friend: He went out with his mates last night.2a person who lives, works or studies with you: André is one of my classmates.a flatmate3one of two animals that come together to make young animals: In spring the birds look for mates.matematematesmatedmating2verb (mates, mating, mated)When animals mate, they come together to make young animals.