verb: To put something out of it's misery. As in the ending of the Disney film Old Yeller, where the young boy puts a bullet between the eyes of his beloved pooch who's gone rabid or old or something.
This girl I hooked up with the other night thinks we're in love or something, I'm gonna hafta old yeller her.
When a blond girl is felating vigorously and she starts foaming at the mouth so in response the sexual recipient pulls out and shoots her in the side of the head.