Sandboxing refers to the action of having sex on the beach with a girl and immediately after blowing your load scooping a handful of sand and throwing it into her vag
Jack: oh I'm coming! (Grabs handful of sand and hurls it at jills vagina) you are a victim of sandboxing!
Jill: ew! Gross Jack!
Jill: ew! Gross Jack!
by Marine9728 July 19, 2013