Globules or strands of stray cum which might have travelled further then you thought & thus don't get cleaned up, which once dry look it / resemble a slug!
Ken "I had a good wank the other day in my mums room, I thought I'd cleaned all the cum entrails up but a few cum slugs had formed on the wall which I hadn't noticed!!"
Frank "what happened, did you mum find them?"
Ken "yeah & it wasn't the first time she had found my cum slugs, so I was in deep trouble!!"
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.