To apply external friction to the labia, usually as a prelude to more intimate sexual acts. Scratchin the lab may be accomplished over the pants such as when dancing or grinding closely, or with no clothes such as prior to cunnilingus or intercourse.
"Hey dude, I heard Kyle brought that girl home last night. Not surprising since he was trying to scratch the lab with her all night at the club."
by Ecogruppenfuhrer February 23, 2025