too big for one's britches

too big for (one's) britches

Overconfident in one's importance, skill, or authority; behaving as if one is more important or influential than one actually is. He's gotten too big for his britches ever since he got that promotion. John's been too big for his britches now that he's been scouted by the NBA.
See also: big, britches

too big for one's britches

Also, too big for one's boots. Conceited, self-important, as in Ever since he won that tournament he's gotten too big for his britches, or There's no talking to Jill anymore-she's just too big for her boots. This metaphoric idiom alludes to becoming so "swollen" with conceit that one's pants or boots no longer fit. [Late 1800s]
See also: big, britches
References in periodicals archive ?
Yet, Coppola, like fellow movie brat Michael Cimino, represents the lesson learned in the "old" Hollywood: One can't get too big for one's britches, or too absorbed in one's own myth.