Rats!

rats

An exclamation of frustration, disappointment, or vexation. Oh, rats—I dropped another screw. A: "Sorry, I won't be able to come this Saturday." B: "Rats! OK, we'll try to get together some other time."
See also: rat
Farlex Dictionary of Idioms.

Rats!

exclam. Oh, damn! Rats! I broke a nail!
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • up against it/the wall
  • up the wall
  • sheesh
  • Sheesh!
  • manual
References in classic literature
"Trained rats!" Manuel Fonseca, the contortionist, exploded in the bar-room of the Hotel Annandale, after refusing to drink with Duckworth.
Michael Brother of Jerry
Poor rats! They seem only to exist so that cats and dogs may gain credit for killing them and chemists make a fortune by inventing specialties in poison for their destruction.
But the rats! they swam the river, they gnawed their way through the thick stone walls, and ate him alive where he sat.
Idle Thoughts of an Idle Fellow
I am the rat-catcher!...Let me pass, with my rats!..."
Phantom of the Opera
"You dirty rats!" Jimmy Cagney walking down Buffalo Avenue.
Rat story last week had legs
Footsteps pounded behind us, and I heard someone yell, "Come back, you dirty rats!" At that moment, I stepped onto the sensor mat in front of the automatic sliding doors.
Rodent Run