noun. The iliacus and psoas magnus muscles taken together, or some muscle which represents them.

noun. The great flexor muscle of the hip joint, divisible into two parts, the iliac and great psoas, -- often regarded as distinct muscles.

noun. A compound muscle composed of the iliac and psoas muscles

"These include the positioning of the pelvis, the front hip flexors (known as the iliopsoas), the abdominals, and gently stretching and contracting the muscles of the lower back."