A loud gagging noise and exaggerated cat-like body movement (much like a black cat on Halloween) made at the same time when one is beyond disgusted by something.

How to properly perform the Halloween cat: Simply stick your 'tail' out, shoot your shoulders up, put your hands out in front like claws, and arch your back. Don't forget to gag as loud as you can.

One could also just say the phrase 'Halloween cat' when the situation does not allow for the loud gagging noise and exaggerated cat-like body movement. The phrase alone is also very effective.
Friend #1- 'I just found out my boyfriend has been cheating on me with my mom!'

Friend #2- 'Halloween cat!'
by HalloweenCat1 March 31, 2011
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