Green’s Dictionary of Slang

1. (US prison) a solitary confinement cell.

1907		J. London Road 103: A couple of them might jump upon him, give him a good beating for alleged insubordination, and throw him into the ‘solitaire’ (the dungeon).
1913		Sun (Glasco, KS) 27 Nov. 3/3: Think of the old ‘solitaire’ — solitary confinement — of Eastern State Penitentiary.
1971		(con. 1920s) J. Brown Monkey Off My Back (1972) 14: Withdrawing money I won in the crooked games I had conducted before going into solitaire.

2. (US black) suicide.

1944		‘Jiver’s Bible’ in D. Burley Orig. Hbk of Harlem Jive.
1949		Monteleone Criminal Sl. (rev. edn).