A wiseacre is someone who pretends to be wise, or when used sarcastically, a wise person. It can also be someone whose actions are funny but also annoying. Other related words are wisenheimer, wise guy, and wiseass.
As you can see by the ngram below, the use of wiseacre has dropped off in recent years in favor of these other alternatives.
Be careful using wiseass, as most still consider this a curse word, albeit one of the tamer curse words.
A wisecrack is a joke, zinger, or ‘crack’; something a wiseacre would say.
Examples
And “let’s play,” a genre of videos in which wiseacres give (mostly older) games the Mystery Science Theater treatment, are already popular on YouTube. [Malaysia Chronicle]
After 35 years, the two have a buddy-comedy chemistry: Westerberg is the grumbly wiseacre, and Stinson, who joined the band at age 13, is the eternal punk-rock kid. [Rolling Stone]
As Woody Allen once put it, he wants to sit at the grownups’ table—and as we all know, he’s got a streak of old-fashioned moral seriousness a mile wide behind that wiseacre smirk. [GQ]
So I wrote this script. I don’t remember much of it, except that Lily had a parrot that was, naturally, a wisenheimer. [PJ Media]
The passengers were told, on at least three occasions, before and after boarding that no peanuts should be consumed at all during the flight as, at the merest hint of peanut dust within the cabin, the girl was likely to suffer a life-threatening allergic reaction. So what happened? Some wise guy four seats or so down from where she was sitting opened a packet of peanuts he had bought in the terminal. And, as announced, the girl went into anaphylactic shock. [Batley News]
She gave President Barack Obama a salute with a Styrofoam cup —a jab at him for saluting Marines while carrying a coffee cup — and delivered one wisecrack after another to a socially conservative crowd that lapped it up. [Politico]