turn-ins

turn in:
1)to give back sth that you no longer need:把你不再需要的东西还回/交回
You must turn in your pass when you leave the building.
离开此楼时请务必将通行证交回来.
2)(especially AmE) to give sth to sb in authority:主要用于美国英语:将某物交给上级(部门)
They turned in a petition with 80000 signatures.他们呈送了一份80000多人签名的情愿书.
Only a few guns have been turned in so far.到目前为止只有少数的枪支交上来了.
I haven't even turned in Monday's work yet.我星期一的作业都还没有交.

3 to achieve a score, performance, profit, etc:
The champion turned in a superb performance to retain her title.
turn in on yourself to become too concerned with your own problems and stop communicating with others

中间加了连字符号，变成名词了。
表示归还或者上交的东西。