a smart alec

a smart alec/aleck

  (informal)
someone who is always trying to seem more clever than everyone else in a way that is annoying Some smart alec in the audience kept making witty remarks during my talk.
See also: alec, smart
References in periodicals archive ?
I know he was trying to help but sometimes empathy can come across as just being a smart Alec.
If a Smart Alec is someone who is clever, what does that make you lot?
I'm not being a smart Alec here but, just in case you ever pass the same train, it was Gianfranco who played for Chelsea.