When you shit on a person(or partner) from a considerable altitude during any sexual act with or without their initial consent. The Seahawk coming from a high altitude and since seattle is always rainy, the shit from a seahawk relates to the rainy season from Seattle thus meaning when you Seattle Seahawk someone you shit on them like rain from a considerable altitude.
BJ: Dang i was boning this party girl the other night and she asked me to get freaky.
Danger: Yeah wat did she want?
Bowser: Dont tell me a boston pancake?
BJ:Na, She asked me to Seattle Seahawk her from the top of her closet!
Danger:You serious dawg??
Boswer: Did you?
BJ: Fuck Yes!!!