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
Patrizio	pah-TREE-tsyo	Italian
Osborn	['ɔzbən]
Carolyn	['kærəlin]
Luka	-	Russian, Serbian, Croatian, Slovene, Macedonian, Georgian, Old Church Slavic
Nathan	NAY-thən (English), na-TAWN (French)	English, French, Hebrew, Biblical, Biblical Latin, Biblical Greek
Bibigul	-	Kazakh