Only one; not one of several. Unmarried or not involved in a stable sexual relationship. Consisting of one part. Free from duplicity or deceit; ingenuous. An individual person or thing rather than part of a pair or a group. A hit that allows the batter to reach first base safely. (especially in tennis and badminton) a game or competition for individual players, not pairs or teams. Choose someone or something from a group for special treatment. Hit a single.