Three accepted meanings:

1 A unit of brightness of nebulae. A nebula is a cloud-like object visible in the night sky, using a telescope or binoculars; think milky squished star. It - a Crab - is, by definition, equal to the brightness of the Crab Nebula, which was seen as a supernova in 1054 A.D., by Chinese and Arab astronomers; also known as the nebula M1 (Messier1).
A Crab has a sub-division millicrab, which any half-competent student of the metric system will be able to tell you is a thousandth-part of a Crab.

2 A hard-shelled crustacean, with a body generally wider than it is long, two pincers, and a wide variation in size, ranging from pea-crabs, about the size of the eponymous vegetable - to spider crabs, which have a claw span of three or four metres/yards in large (= old) specimens.

3 Pubic lice. This indicates that you may not have been too careful aboutyour fuck-buddies.
1 The new nebula is about five hundred and twenty millicrabs - say half the brightness of the Crab Nebula - said the little blonde astronomer; plainly, she didn't seek to sensationalise this new discovery.

2 Crabs can be caught in many coastal waters - but be careful picking them up, as they can nip.

3 'That damned soccer-jock gave me crabs - he must have shagged Brutus last week!' said Pandora with resignation, whilst counting her plentiful takings.
by railtracksurvivor May 01, 2009

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offensive term for Crips
yo, that crab is a pussy
by me December 22, 2003

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a pubic louse(usually plural)
That girl had crabs. Why would you even think about having sex with her?
by Light Joker October 12, 2004

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1. A person who does not want another person to succeed by showing the following actions: Disloyalty, Jealousy, Slander, Two-faced behavior.

2. A person who uses another for personal gain or self gratification.

Synonyms: Hater, Back Stabber Leach Free-Loader
1. "Just like crabs in a bucket, won't nobody let nobody up"

2.I told you that "Crab" was not going to come to your show.

3. I loaned her some money and I know she received her bonus, and that "Crab" has not even mentioned my money
by 1Real813Beauty October 15, 2010

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little bugs that crawl and bite your nut sack
me : DUDE! guess what !!??
jon: what!!??
me : my sack itches
jon: ok why are you telling me ?
me : tell your sleezy douche bag mom i said thanks for the crabs!
by vagine ridar January 21, 2008

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Little animals found on the beach.
Samantha, don't talk to strangers, you'll get crabs.
by Rob Templin February 13, 2003

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Abbreviation for Crips Respect All Bloods.
Fakeass gangstaz disrepecting they flags by callin em rags. A rag is something you clean with. Only people carryin em are CRABs.
by CK October 03, 2004

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