- (使)落进；(使)往里坍塌：
The roof of the theatre dropped in on them.
剧场屋顶坍落在他们身上。
- 偶然(或顺便)走访(或访问)(on)；逐渐进入：
Drop in sometime tomorrow.
明天什么时候请顺便来一下。
Drop in on me at any time.
什么时候都可以来我这里。
She often dropped in for coffee.
她常过来喝杯咖啡。
- [口语](有选择地)加入；愿意(或决心)参加：
Many students are dropping in to classes.
很多学生在上各种班。
- 【戏剧】放下(吊幕)，吊装布景：
They dropped in the scenery for the next act.
他们为下一场戏放下了布景幕。
- 投入：
You can drop letters in through the hole in the door.
你可把信从门上洞口投进去。