v.
An expression you use when you are
high (or on some occasions it has been
done sober when a person gains a burst of energy and does not what to do with it). Usually it resembles an imitation of a raptor while saying the proverbial "gnack gnack". It can be spelt either gnack gnack or gnak gnak.
At the
party, Buttons put his hands up
like claws, looked around the room, and
said "gnak gnak".