slack

slack off/up

1. 松劲; 懈怠

Don't slack off in your studies.

不要荒费你的学业。

2. 减缓; 变呆滞

The train slacked off as it came into the station.

火车进站时将速度减慢了。

take up the slack

1. 收紧松弛的绳索

The sailors pulled at the rope to take up the slack.

水手们拉起绳索把它收紧。