get too big for (one's) britches

get too big for (one's) britches

To become overconfident in one's importance, skill, or authority; to start speaking or 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. Honestly, John got too big for his britches as soon as pro teams started scouting him.

See also: big, britches, for, get

Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.