A smotherbox (or smothering box) is a type of dungeon furniture similar to a queening stool. It may be used in facesitting, where a man or woman acting in a Dominant role sits upon the face of a person acting in a submissive role, to emphasize the superiority setting. This may include receiving oral sex from the submissive person.
A smotherbox has two openings. One is in a vertical side of the box for the neck of the person who has her/his head inside the smotherbox. The other is on top of the box to expose the face of the person who has their head in the box. The inside of a smotherbox is often padded to provide support for neck of the person in the box, and to prevent their head from moving. The padding may also muffle noises from outside of the box, thereby relaxing the one being sat upon and leaving more room in his/her mind for other senses.