n.1 a diamond or other gem set by itself.
2 a ring having a single gem.
3 a game for one player played by removing pegs etc. one at a time from a board by jumping others over them until only one is left.
4 US PATIENCE 4.
5 any of various extinct dodo-like flightless birds of the family Raphidae.
6 any American thrush of the genus Myadestes.
Etymology: F f. L solitarius (as SOLITARY)