Green’s Dictionary of Slang

1. (US black/teen) a large cannabis cigarette.

2002

A. Westbrook Hip Hoptionary 120: Scooby-Doo: marijuana rolled in cigar paper after tobacco has been dumped from its casing.

2. (US campus) a person who never puts on weight, despite eating lots of food.

1996

Eble Sl. and Sociability 42: The repetition of vowel sounds can be heard in [...] scooby-doo ‘someone who eats a lot and never gains weight’.

3. (US black) a firearm.

2000

Ebonics Primer at www.dolemite.com 🌐 scooby-doo Definition: a firearm Example: Boo Hoo, where ya gonna run to when I pull out the Scooby-Doo?