1. conceited; swelled with self-importance; too haughty for one’s status or age

1. I used to like George, but now I think he’s grown too big for his britches.

2. Bill’s getting a little too big for his britches, and somebody’s going to straighten him out.

3. You’re too big for your britches, young man! You had better be more respectful.

4. He's been getting a bit too big for his boots since he got that promotion.