bitchy pants

noun2

1. •
   (informal, figurative) A notional pair of trousers or underwear worn by someone when acting bitchy.

   • We asked him to take off his bitchy pants and put on his big-boy pants.
2. •
   [before a noun] (vulgar, offensive) A currently irritable or habitually unpleasant person.

   • I should just trust him, shouldn't I? I mean—what does Alicia Bitchy-pants know about anything? — 2002