Top definition
The stain left in your draws or on a keyboard after a good Jackoff.
Man i hope mom dosen't notice that jack stain on wash day.

Nice Jack Stain man.

WOW!!! look at the size of that Jack Stain.
by JerkSquirt July 10, 2009
Happy St. Patties Day!
A stupid person described by a spot or spots of ejaculation.
"Paulie was busted after trying to buy weed from an undercover cop...he is a real jackstain."
by Shawna123 August 08, 2005
Happy St. Patties Day!