dumb smartass

Dumb Smartass (not to be confused with smart dumbass) is someone who has horrible grades in school. However, outside of school they know everything and can tell you the square root of 6916541845383 in 5 seconds without a calculator

During test: Oh lord, I can't remember what countries Napoleon invaded
At home: Napoleon invaded Spain, And Russia among other countries after retaking France
His friend: What the f*** you couldn't remember that during the test you're such a Dumb Smartass