sandbagger

noun [专属名词]以沙袋为凶器袭击他人的恶徒

If you pretend not to know how to play pool so your opponent will bet money on a game, you're a sandbagger.
如果为了让对手在比赛中下注而假装自己不会打台球，那你就算是个“赌徒”了。