1 [count] : a person who lives with you, works in the same place as you, etc. — usually used in combination with another noun ▪ We have been office mates for 10 years. [=we have worked together in the same office for 10 years] — see also classmate, flatmate, housemate, playmate, roommate, running mate, schoolmate, seatmate, shipmate, soul mate, stablemate, tablemate, teammate, workmate 2 [count] : either one of a pair of animals that are breeding
▪ One bird remains at the nest while its mate hunts for food. 3 [count] chiefly US : a person's husband, wife, or romantic or sexual partner
▪ He was finding it difficult to find a mate. ▪ an ideal mate 4 [count] chiefly US, informal : either one of a pair of objects
▪ I can't find the mate to this glove. 5 [count] : an officer on a ship who has a rank below the captain
▪ a first/second/third mate 6 [count] chiefly Brit, informal : a friend
▪ Me and a couple of mates of mine went round to the pub. ▪ She and I have been best mates for ages. — often used as a friendly way for one man to address another man ▪ Got a light, mate? 7 [count] chiefly Brit : an assistant or helper
▪ a plumber's mate ▪ an electrician's mate 8 [noncount] : checkmate