sit in 1. 〈主英〉代人临时照看小孩；代人暂时照料 I shall sit in for you while you go to the shops. 你去买东西的时候，我将代你照料一下。 2. 参加静坐罢工(或示威) Hundreds of people are sitting in at the city hall. 好几百人在市政厅参加静坐示威。 3. (作为非正式队员)参加乐队的演奏(或演唱)，客串 On these occasions he might sit in on drums. 逢到这些场合，他就可能参加乐队打鼓。 Before the war any player could walk into a club and sit in with the band. 战前，随便哪个演奏者都能到夜总会客串参加演出。