smarty pants
[noun pluralbut singular in construction]
Synonyms: smart aleck, know-it-all, *smartass, smarty, wiseacre, wisecracker, wise guy, wisehead, wisenheimer

[TahlilGaran] English Synonym Dictionary ▲

smarty-pants noun

1. a person who thinks they are very clever and likes to show people this in an annoying way

[TahlilGaran] English Dictionary ▲

a smarty pants
[informal]
someone who is always trying to seem more clever than everyone else in a way that is annoying.
Cindy, the little smarty pants, will be the first to tell us where we went wrong.

[TahlilGaran] English Idioms Dictionary ▲