"Letting off steam" generally means to release anger or frustration, usually by expressing it in some way. For example, someone might let off steam by yelling or venting to a friend.
1. After work, I like to go for a run to let off steam.
2.
You
just need to let off steam by screaming into a pillow.
3.
Playing
video games is a great way to let off steam.
4.
I
lift weights after work to let off steam.
5.
We
go jogging to let off steam on a regular basis.
6.
I
spent the whole afternoon complaining about my boss. I just needed to let off steam.