A sexual technique / practical joke.
For a male to pull his own rod and shoot his load on someone. This male must be stationed by a window ledge, on a bridge, on a tree or basically any height by which innocents may pass. On the point of ejaculation, said male must aim his spray at a passer-by, creating a similar scenario to a pigeon crapping on this passer-by. When the passer-by looks up, instead of finding a snarsy, giggling pigeon, they will instead find a dangling penis and ballsack and potentially an extra drop or two.
*Note* This can also become a couples event. As long as the partner has a steady hand and understands the tempo at which the "shooter" likes to masturbate at.
Passer-by (To self): "awww, not a pigeon crap, on my new Armani suit! I've got an important international business meeting in a minute. (Looking up into the tree he is passing)
Naked tree-man: "You just hit with The Pigeon BITCH!"
Passer-by: "You don't mean to tell me this is semen? Oh SHIT, OH SHIT"
when you jerk off out a window or off a bridge
i gave that chick downstairs the pigeon.