Chomp

Verb
1. A reaction to a statement or question in a non positive or accepting sense.

If someone calls you out and you respond with 'what' or 'no' or such like, verbal or non-verbal, they can say chomp and laugh in your face.

>>> Hey you look like the creepy guy from that movie.

<<< What! No I don't!
>>> Chomp! Bahahahaha

A chomp can be avoided with agreement
>>> Hey you look like the creepy guy from that movie.

<<< Cool