To blow off steam means to get rid of your anger, excitement, or energy in a way that does not harm anyone by doing something active. Also possible: Let off steam.

For example:

Going for a run after a stressful day or talking to a friend to vent frustrations are examples of blowing off steam. 

If you’ve had a particularly long week, maybe you stay out a little past curfew to blow off steam.

The beach, for many of us, is a place to relax and blow off steam.

So I quickly changed into jeans and a T-shirt for a walk on the Heath, to blow off steam.

The web has been called many things; among them, a net of hate where people blow off steam in unfortunate ways.

Tradução: relaxar, descontrair, extravasar, espairecer, esfriar a cabeça, liberar energia.