sacrospinous ligament

noun

sa·​cro·​spi·​nous ligament ˌsā-krō-ˌspī-nəs-, ˌsak-rō- 

: a ligament on each side of the body that is attached by a broad base to the lateral margins of the sacrum and coccyx and passes to the ischial spine and that closes off the greater sciatic notch to form the greater sciatic foramen and with the sacrotuberous ligament closes off the lesser sciatic notch to form the lesser sciatic foramen