What is Zip Thunk?
1.
Sound made from unzipping the pants and a large member hitting the floor. Normally used when someone makes you mad and you want to get them back or do something bad to them.
I am gonna get you back. Zip thunk.
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2.
Comment made to infer homosexual activity on the part of another, usually made in the middle of speech by the other or during a movie or television show