When someone is really, really, REALLY high or drunk. Auditory and visual functioning are impaired to comedic levels and the individual expresses a desire to stay in a place where other people want to leave OR leave a place where everyone is staying because the alcohol and drugs are impairing their thought processes and physical stability.
Jason Red was already clacked, but the Twerk Queen twerking on him pushed him over the edge and made him the party early. "I'm clacked! I got graduation tomorrow and I'm hungry."

Billy Blue was so clacked that he had to have an escort (Zack Black) to prevent security from kicking him out because of his boisterous and rowdy behavior.
by STH June 28, 2013
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Verb. For one to swing one's scrodum back and forth until a sound is heard. The sound can either be high pitched like a slap, or it can be deep like your ball sack is jelly. While swinging your fellow peers encourage you to trust forward harder, propelling the sack to make an intense clacking noise. The person who makes the louder noise with their ball bag is the champion of NYM&FR.
I thought it could never be done, it was terrible, yesterday I clacked so hard my sac started to bleed profusely. I screamed but luckily my friends were there to massage the pain away.
by M&F Race May 12, 2005
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The action of getting ran into on a ski slope. Usually a result of a gaper taking slow, unpredictable turns that take up the entire mountain.
Dude that gaper made a turn out of nowhere and I clacked him!
Sorry I'm late, I almost clacked this gaper back there.
by Reih April 25, 2008
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Most commonly used to describe aggressive, carnal sex which harkens to the exaggerated "ass-clap" sounds of mainstream pornography. Commonly accompanied with obnoxiously loud clapping of the hands for effect.

Its long form, "clack-a-lack," may also be used for special emphasis.

Rhymes with "gak," which, besides being an archaic Nickelodeon product, is a slang word for semen and/or ejaculating. Thus, to say "clack 'n gak" would be to suggest a "down and dirty" coital session in which the male only concerns himself with his own ejaculation and subsequent bragging rights.

May also be used to suggest any contact between two hard surfaces, usually instigated in an aggressive fashion.
Women (or men on the receiving end) may find the term "clack" offensive, as they are often referred as the pronoun "it" or "that" rather than named outright.

Thus,

"Dude, did you clack that shit?"
"Hell yeah I clacked it!"

Sounds much better than:

"Dude, did you clack her?"
"Hell yeah I clacked her!"

If the subject must be named in the sentence, then the pronoun "it" is still included and precedes the subject:

"Oh man, I'd love to clack it with the Olson twins."

Examples of non-sexual uses:

"Somebody tell this guy to scram before he gets clacked in the jaw."

"Damn, he clacked it out of the park!"
by jefeljefe January 4, 2010
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Used in "American Idol" fandom, specifically by Clay Aiken fans: Clay photos, stories, performances, etc., that serve as a fan's "Clay fix". Derived from "crack."
"Dear God, did you see Clay's Rolling Stone cover? That was some major clack."
by Tak, the Hideous New Girl December 29, 2004
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Hoping for a humerous release of wind you inadvertently fill your underpants with solid, rendering them unusable
Husband: "Ooops!! I just clacked my trunks"
Wife: "Oh, not again darling?! Here's your spare pair, now go throw those filthy ones in the bin"
by panda-niku May 17, 2010
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