"Taking a dab" or the act of dabbing in this instance, is a form a marijuana use, by extracting the active ingredients and isolating them from the plant matter, this results in a Wax, sugary, oily, substance usually of a light amber color resulting in THC levels sometimes over 90% along with the original (if there extracted properly) terpenes and other cannabanoids that give that strain of cannibis is specific flavor/aroma and effects, it is often vaporized from a bong like, glass contraption often reffered too as a "dab rig" or "oil rig", but instead of a bowl, a small dish shaped, cup shaped piece, called a banger or nail, made from either Ceramic, titanium, or quartz, heated with a torch, as too vaporize your dab on contact.
"Hey bro, wanna take a dab with me later?? Get HIGH AS FUCK??"