an adult male human being: a young/tall man men and women the man in the green jacket For a very long time, only men could join the armed forces. Steve can solve anything - the man's a genius. an adult who lives and identifies as male though they may have been said to have a different sex at birth: Mark is a trans man (= a man who was said to be female when they were born). Their doctor encouraged them to live as a man for a while before undergoing surgical transition.