Somewhat inadvertent "crunches," or quick contractions of the abdomen, that some women perform during orgasm; especially during multiple orgasms.
Alternatively known to as "O-sit-ups."
"Oh! Oh! Oh! Oh! Oh! Oh! Oh!" Tami cried during her "workout." She was too lazy to get up, put on spandex, lie on the floor, and do actual crunches, and preferred instead to stay in bed while Josh gave her o-crunches.