Green’s Dictionary of Slang

(US drugs) to indulge in narcotics to a small, supposedly non-addictive degree.

2009		W.D. Myers Dope Sick 54: I slipped from dibbing and dabbing into drugs, from weekend parties to really getting wired up.
2012		W.D. Myers All the Right Stuff 179: ‘[W]hen I was dibbing and dabbing and got caught up, I couldn’t get no help’.