"Understanding how to play shorthand games (six or fewer people) is important to becoming a winning poker player."

"By shorthanded, I am referring to situations with five or fewer players."

"While 6 players doesn't constitute a shorthanded game in the strictest sense of the term..."

"Un shorthand, es decir, una partida con menos de 6 jugadores, requiere una mezcla de habilidades técnicas y personales..."

Everyone agrees that less than 6 players make a shorthanded game. I'd probably leave in the source term and add the explanation, as above.