too big for one's breeches

Adjective

• (used colloquially) overly conceited or arrogant
  • a snotty little scion of a degenerate family-Laurent Le Sage
    
  • they're snobs--stuck-up and uppity and persnickety
    

Related words

• Synonyms: 
  bigheaded , persnickety , snooty , snot-nosed , snotty , stuck-up , uppish