Where a female squats over an unsuspecting person's face and spreads their legs and vaginal lips/flaps. They then lower themselves right down so the lips/flaps are on both sides of the person's nose. From the unsuspecting person's point of view this may look like a large stingray slowly descending onto their face. Lip size may affect safety, be careful not to block their breathing holes.
Oh damn when he fell asleep Kristine totally stingrayed him!