A person who unintentionally rubs people the wrong way for her own pleasure, who delights in scraping against the grain and rubbing raw other people's sensibilities, when her goal could more easily be accompished with a gentle and considerate approach. This personality type tends to be volatile, and is also known as nifer.
Police Officer: "Lady I'm gonna have to write you a ticket.."
Zester: "Go ahead, you fat pig bastard; it's no wonder everyone hates cops. Can't touch this!! Woo hoo!!" (dances wildly in circles waving right hand in air)
Zester: "Boss, can I leave early today to go get a fudgesicle, you moronic fairy? Ha, just kidding."
A fart that burns coming out, clears the room and makes others gag.
"I just let a zester go"
"Man that zester really put me down"