smart alec
noun (British English)(North American English usually smart aleck)
(also smarty-pants)
(also British English, offensive smart-arse)
(also North American English, offensive smart-ass)
(informal, disapproving)a person who thinks they are very clever and likes to show people this in an annoying way 自诩聪明的人；好逞能的人 Word Originmid 19th cent.: from smart + Alec, diminutive of the given name Alexander.