Formerly, a party in which everyone brings their own alcohol, which upon entry is taken and poured into a large vat with the rest of the booze. This concoction is served in cups from a tap at the bottom of the vat, and has become less popular over the years.

More recently, a vat party is when several attendees bring a supply of recreational pills to a party, preferably of several kinds or types, and the pills are all mixed into a bowl where adventurous attendees can investigate potential combinations for a particular effect, or discover their own. Many people die at such parties, especially when mixing the pills with alcohol.
Five people in my family had surgery this past year and I'm gonna host a hell of a vat party with their leftover scripts!
by spider kids February 24, 2011
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Someone who is a boz. Someone who can eat my klir. Someone who has no inqnasirutyun. If you ate a qfur, xlesh if you are a cchox, choqox or etc., you are a vat txa and can eat my jujulik.
Person One (lav axper): Mech axper today at school I made new friend, his name is flan fstan.

Person Two (mech apxer): You not good ay txa. Dont talk to him again hes a vat txa.
by Lav Txa Gevorik February 3, 2023
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South African expression exhorting someone to take on someone else aggressively
In a rugby game, the opposing wing is running with the ball full steam towards the fullback. Someone in the crowd will yell at the fullback: "Vat hom Flaffie!"
by Shaul B March 8, 2017
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Artery clogging lunchtime fare, preferably re-heated from the previous evening's colon lubricating dinner selection, and consisting only of the tangy "meat" portion.
That Vat O' Beef is going to evacuate his bowels!
by Ah the memories! December 17, 2003
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