The weight of any quantity of a substance before it is dried. In particular, a dishonest practice by drug dealers in which a dealer will sell marijuana that is not entirely dry, and therefore much heavier. If you buy wet weight weed you will get much less high per gram. The practice of selling wet weight is related to other dishonest practices such as selling cut drugs.
Man I'm killing it, riding in that brand new
Swimming through the streets, looking like I'm Shamoo
In that big body, with the wet paint
I got some pocket change, from selling wet weight
-lyrics from Im Good by Clipse ft Pharrell