He was slow-playing in the poker game to make his opponents think he had a weak hand.

slow-playing 是由形容词 slow（慢的）和动词 play（玩、打）组成的复合动词，加上 -ing 变成现在分词形式。slow-play 指在扑克等游戏中故意放慢节奏、假装犹豫的行为，目的是迷惑对手。slow-playing 在这里表示"故意慢打"的策略。