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]
Words nearby too big for one's britches
tontine,
tonus,
tony,
too,
too bad,
too big for one's britches,
too close for comfort,
too close to call,
too good to be true,
too little, too late,
too many cooks spoil the broth