Extreme hot or cold temperature. Usually defined as "colder than zip's ass" or "hotter than zip's ass". Refers to 0 degrees F or lower or 90 degrees F or above.
The act of your dick unintentionally falling out of the front flap in your underwear. NOT to be confused with the more ambiguous dick slip
Brad: Ow, fuck! Yo Chad, wait up!
Chad: What’s wrong bro, can’t keep up?
Brad: Nah bro, I had a zip slip!
Chad: Ouch, man! Hope you didn’t chafe against the zipper too bad!
Brad: All good, dude. This one was far from my worst.
The end result of when you take an ordinary stick and tie a plastic bag very tightly to the end of it. You then proceed with lighting the plastic on fire until it melts thoroughly the lift the stick high into the air. The platic will begin to drip off and with each drip, it gets super-cooled and making a nifty little "zipping" sound.
We made many zip sticks at our bon fire last night. Pascal thought he'd be cool to catch one of the flamming drops of plastic. He regretted it 3 milliseconds later.