a wise guy

(American & Australian informal) also a wise-ass (American very informal!)

someone who is always trying to seem more clever than everyone else in a way that is annoying Okay, wise guy, if you're so damned smart, you can tell everyone how it's done! He's just some wise-ass who thinks he knows all the answers. (American & Australian informal)

See an old head on young shoulders

Common Names:

Name	Pronounced	Usage
Fridtjof	FRIT-shof (Swedish), FRIT-yof (Swedish)	Swedish, Norwegian, Danish
Giustina	joos-TEE-nah	Italian
Lysander	-	Ancient Greek (Latinized)
Tessa	['tesə]
Brenton	BREN-tən	English
Hyacinth	['haiəsinθ]