[TA] the lower opening of the true pelvis, bounded anteriorly by the pubic arch, laterally by the rami of the ischium and the sacrotuberous ligament on either side, and posteriorly by these ligaments and the tip of the coccyx. SYN: apertura pelvis inferior [TA], apertura pelvis minoris, fourth parallel pelvic plane, inferior pelvic aperture, pelvic plane of outlet, plane of outlet.
