sol·i·taire / ˈsäləˌter/ • n. 1. any of various card games played by one person, the object of which is to use up all one's cards by forming particular arrangements and sequences. 2. a diamond or other gem set in a piece of jewelry by itself. ∎  a ring set with such a gem. 3. either of two large extinct flightless birds (family Raphidae) related to the dodo, found on two of the Mascarene Islands until they were exterminated in the 18th century. 4. a large American thrush (genus Myadestes) with mainly gray plumage and a short bill.

solitaire in the early 18th century, a person living in seclusion, a recluse; also, a precious stone, usually a diamond, set by itself.

From the mid 18th century, the term was also given to a game for one player, as a form of patience, or a game played by removing pegs one at a time from a board by jumping others over them from adjacent holes, the object being to be left with only one peg.

The word comes from Latin solitarius ‘solitary’.