too big for 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 pro teams.
See also: big, britches, for
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

too big for one's britches

Rur. too haughty for one's status or age. Bill's getting a little too big for his britches, and somebody's going to straighten him out. You're too big for your britches, young man! You had better be more respectful.
See also: big, britches, for
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.

too big for (one's) britches

Overconfident; cocky.
See also: big, britches, for
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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References in periodicals archive ?
According to Tmz.com, the cast members of the reality show were all in a VIP suite at the Gulf Stream Race Track in Hallandale, Florida last Saturday when Crooks called out William, who the other participants feel has become "too big for britches".