facesitting

A character sitting on or straddling the face of another character. Characters often perform oral in this position.

If the character on top is positioned in the same direction, facing away from their partner, the position becomes reverse_facesitting.
If a character is about to sit on the face of the viewer or another character, use imminent_facesitting
If the receiving character is kneeling or standing, and has the other character's butt shoved into their face, this is stinkface, not facesitting.
Depending on the context, facesitting can be seen in comedic or humorous situations without carrying a sexual character.