The act of ejaculating onto/into your partners pilliowcase. Then when your partner wakes up the next morning your invisible ink has dried, leaving a white film on the pillowcase.
The reason its the "Seattle" Sleeper is because the city always gets a light dusting of snow that you can only really see in the morning.
I woke up and my partner had left a Seattle Sleeper on my pillow, it took a little more effort than usual to pull my face away.
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.