A fench is someone who is old, and bloated. Otherwise known as the adorable little man from "Up!" Can be used positively, negatively, and neutrally!
Adjective: Don't act so fenchy and let the handicapped person use the handicapped parking spot!
Verb: Go fench youself!
In other words, an act of aggression so successful that full revenge is impossible.
1. "I've just witnessed a particularly amusing fench"
2. "I've just been fenched"
3. "You're worse than a bastard - you're a fencher!"