Green’s Dictionary of Slang

(Aus./US drugs) cannabis that causes one to become tired and lethargic.

2002		Bud Smokers of America ‘Stoners’ Dict.’ 🌐 Dregged [AU] – To become tired and lethargic after smoking. Dreggin – It means like u’r not really high anymore but your all tired and dregged out, man, I don’t know how 2 explain, nevamind. Dreggy [AU] – Cannabis that causes one to become dregged.
2002		‘Dictionary’ at members.rogers.com 🌐 Dregged: To become tired and lethargic after smoking cannabis. Dreggy: Cannabis that causes one to become dregged.