too big for one's breeches vs bigheaded

too big for one's breeches and bigheaded both are adjectives.

Word	Noun	Adjective	Verb	Adverb
too big for one's breeches	No	Yes	No	No
bigheaded	No	Yes	No	No

As adjectives, too big for one's breeches and bigheaded are synonyms defined as:

too big for one's breeches and bigheaded: (used colloquially) overly conceited or arrogant

Other synonyms of too big for one's breeches include persnickety, snooty, snot-nosed, snotty, stuck-up, uppish.

too big for one's breeches (adjective)	bigheaded (adjective)
(used colloquially) overly conceited or arrogant	(used colloquially) overly conceited or arrogant