When a woman sits on her partner's face as an act of domination, with one or more of three possible goals: 1. Smothering, breathplay; 2. Scentplay, forced to smell; 3. Forced oral sex.
For 1&2, the sitter may be in any stage of undress. For example, either fully clothed, in panty hose panties or nude.
For 3, most often nude.
It is not uncommon for the sitee to be bound or movement restricted in some way.
She preferred using a smotherbox for face sitting