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1.
1. Overconfident or cocky.

2. Believing that you know everything to the point to where it can harm you or work against you.

3. Assuming or Showing knowledge/intelligence to the point where it can harm you or work against you.

4. Believing that you know something you really don't, which could get you in trouble.

This can also mean too good for your own good or too big for your britches.
Don't be too smart for your own good. It has it's own way of catching up with you.

Most of the young and inexperienced is too smart for they own good.
by Mr. Terrence L. Trezvant April 15, 2007
 
2.
1. Believing that you know everything to the point to where it can harm you or work against you.

2. Assuming or Showing knowledge/intelligence to the point where it can harm you or work against you.

3. Believing that you know something you really don't, which could get you in trouble.

This can also mean too good for your own good.
Don't be too smart for your own good. It has it's own way of catching up with you.

Most of the young and inexperienced is too smart for they own good.
by Mr. Terrence L. Trezvant January 10, 2007