Definition

Street slang for heroin, named for its potent, fuel-like punch. Not to be confused with the actual fuel, the Vin Diesel actor, or those jacked gym bros who also get called diesel. Context is everything.

Example Usage

The cops busted a dealer moving diesel on the corner last night.

Source: Urban Dictionary (https://www.urbandictionary.com/define.php?term=diesel&defid=4074)