What is "ischial tuberosity"

n. (context anatomy English) Each of the two lower extremity of the pelvis in humans (and other animals), on which the weight is placed while sitting and which are covered by the gluteus maximus while standing.

The ischial tuberosity (or tuberosity of the ischium, tuber ischiadicum), also known informally as the sitz bone, or as a pair the sitting bones is a large swelling posteriorly on the superior ramus of the ischium. It marks the lateral boundary of the pelvic outlet.

When sitting, the weight is frequently placed upon the ischial tuberosity. The gluteus maximus provides cover in the upright posture, but leaves it free in the seated position.