A strange phenomenon which occurs when you are watching porn with your girl on a leather couch. As she begins to get wet with excitement (at this point she is probally naked or bottomless) she will leave a sticky streak of lube from her vagina as she moves across the couch, resembling a trail of slime left by snails and slugs
Deb got so turned on by the lesbo video she left a snail trail across my new couch.
The female form of the bagdrag, the snailtrail is the sliding of one's poonanny across the forehead of an unsuspecting intoxicated or sleeping victim. The snailtrail is best performed during ovulation when discharge is thicker and richer. Note: can result in injury if the snailtrailer is not stealthy.
Hey look, Kira is sleeping peacefully, let's start her morning off right with a snailtrail.