Definition
To go to bed for the purpose of sleeping.
指上床睡觉。
I've been working all day; it's really time to hit the hay.
我已经工作了一整天；现在真的该上床睡觉了。
The kids were exhausted from playing, so they decided to hit the sack early.
孩子们玩得太累了，所以他们决定早点睡觉。
After this movie, I plan to hit the hay immediately.
看完这部电影后，我打算马上上床睡觉。