blow off steam, to

blow off steam

Also, let off steam. Air or relieve one's pent-up feelings by loud talk or vigorous activity. For example, Joan's shouting did not mean she was angry at you; she was just blowing off steam, or After spending the day on very exacting work, Tom blew off steam by going for a long run . This metaphoric term refers to easing the pressure in a steam engine. [Early 1800s]
See also: blow, off, steam
The American Heritage® Dictionary of Idioms by Christine Ammer.

blow off steam

verb
See blow off some steam
See also: blow, off, steam
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions

blow off steam

To give vent to pent-up emotion.
See also: blow, off, steam
American Heritage® Dictionary of the English Language, Fifth Edition.

blow off steam, to

To let out one’s frustration or anger, usually by shouting. The term comes from the early days of railroading, when locomotives had no safety valves. When the steam pressure built up, the engineer would pull a lever that would blow off steam and prevent an explosion. It was transferred to human wrath in the early nineteenth century. “The widow . . . sat . . . fuming and blowing off her steam,” wrote Frederick Marryat (The Dog-Fiend, 1837). See also let off steam.
See also: blow, off
The Dictionary of Clichés by Christine Ammer
See also:
  • need to let off (some) steam
  • need to let out (some) steam
  • let out (some) steam
  • relieve
  • relieve (one's) feelings
  • relieve your feelings
  • rammy
  • blow off (some) steam
  • blow off some steam
  • blow off steam