A treat for her. Her lover places two or more well lubricated and inspection gloved, fingers, into her anus, then firmly massages her G-spot and it's related squirt glands, through several thick layers of muscular vaginal and anal tissue, against her pubic bone. She goes off like a gun if you do it right! Don't spare the lube! See also asspuppet, cornweasel, etc.
Maggie had never experienced the buttpuppett, and was anxious to see if she would squirt when she was bound and played, by the other girls in her cabin.