In my mind, the opposite of smart is stupid.
Definitions from Wiktionary, a free dictionary
- exhibiting social ability or cleverness
- exhibiting intellectual knowledge, such as that found in books
- good-looking, as a smart outfit
- cleverly humorous, in a way that is rude and disrespectful however; wise guy.
- He became tired of his daughter's sarcasm and smart remarks.
- (exhibiting social ability): backward, boorish, dull, inept
- (exhibiting intellectual knowledge): ignorant, uncultivated, simple
- (good-looking): garish, outré, tacky
- (exhibiting social ability): bright, capable, sophisticated, witty
- (exhibiting intellectual knowledge): cultivated, educated, learned
- (good-looking): attractive, chic, stylish, handsome