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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a form of sex in which the male (or a female with complete strap-on genitalia) repeatedly inserts their balls into their partner's asshole. The balls and asshole are each lubricated to ensure full pleasure for both participants.
To stimulate their dormant sex life, the husband surprised his wife during their weekly sex by getting behind her, and clacking her into submission.
by clackmaster3000 November 23, 2011
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When double-penetrating a bitch, it's the sound of your balls hitting your friends balls on the other side of the bitch.
Larry and I clacked this ho last night.
by Jizzoint March 22, 2004
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Another word spoken in admiration for women's breasts.
Must be used in admiration and as a compliment. You see a girl who is well built and you say; Hmmmm, baby got CLACKS!
by Big Daddy Corleone September 8, 2011
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