The term shorthanded is used in the poker vocabulary to describe a poker game that is played with fewer than nine or eight players. Most commonly, a shorthanded game is the one with six players at the table, but it can also be any number under that, down to three.
The term shorthanded is used to distinguish these games from full-ring (i.e., 9-handed) games. This distinction is important because these two formats play significantly different.
In a shorthanded 6-max game, players can play a lot more hands before the flop, and the play is generally more aggressive. Full-ring games are usually more passive, as players are forced to wait for stronger hands and do not try to steal the pot so often.