too big for your boots
too big for (one's) boots
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 boots ever since he got that promotion. John's been too big for his boots now that he's been scouted by pro teams.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
too big for your boots
BRITISH, INFORMAL ortoo big for your britches
mainly AUSTRALIAN, INFORMALIf someone is too big for their boots, they behave as if they are more important or clever than they really are. Note: In the second expression, `britches' is also spelled `breeches'. I was often accused of being too big for my boots. If you ask me, he's too big for his britches since he struck it rich. Note: You can also say that someone gets too big for their boots or gets too big for their britches. In Britain, people seem to have a thing about not letting someone get too big for their boots. Getting too big for their britches, kids these days. Think the whole universe should revolve round them. Note: Britches are trousers which reach as far as your knees.
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012
too big for your boots
conceited. informalFarlex Partner Idioms Dictionary © Farlex 2017
too ˌbig for your ˈboots
(informal) thinking that you are more important than you really are: His political rivals had decided that he was getting too big for his boots.Farlex Partner Idioms Dictionary © Farlex 2017