1. An arrest; a pick-up by police on suspicion. 2. A report or lock-up for violation of prison rules.

- american underworld dictionary - 1950

A grab is the basis of the majority of tricks in skateboardin, snowboarding and rollerblading. It involves simply reaching down, grabbing hold of a part of your board/blades and holding it for as long as you can (in most cases). I am completely clueless with rollerblading, but the following is a list of the most common grabs in skate and snowboarding:

Indy
Mute
Nosegrab
Tailgrab
Stalefish
Roastbeef
Melancholy
Rocket Air
Judo (skateboarding only)
Japan Air
Benihana (skateboarding only)
Madonna (skateboarding only)
Tweak

Grab (?), n. [Ar. & Hind. ghurb crow, raven, a kind of Arab ship.] Naut.

A vessel used on the Malabar coast, having two or three masts.

 

© Webster 1913.

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Grab (?), v. t. & i. [imp. & p. p. Grabbed (?); p. pr. & vb. n. Grabbing.] [Akin to Sw. grabba to grasp. Cf. Grabble, Grapple, Grasp.]

To gripe suddenly; to seize; to snatch; to clutch.

 

© Webster 1913.

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Grab, n.

1.

A sudden grasp or seizure.

2.

An instrument for clutching objects for the purpose of raising them; -- specially applied to devices for withdrawing drills, etc., from artesian and other wells that are drilled, bored, or driven.

Grab hag, at fairs, a bag or box holding small articles which are to be drawn, without being seen, on payment of a small sum. [Colloq.] -- Grab game, a theft committed by grabbing or snatching a purse or other piece of property. [Colloq.]

 

© Webster 1913.