Webster's 1828 Dictionary
PSOAS
n.[Gr. ] The name of two inside muscles of the loins.
Webster's 1913 Dictionary
PSOAS
Pso "as, n. Etym: [Gr. psoas. ] (Anat. )
Defn: An internal muscle arising from the lumbar vertebræ and inserted into the femur. In man there are usually two on each side, and the larger one, or great psoas, forms a part of the iliopsoas.
New American Oxford Dictionary
psoas
pso as |ˈsōəs ˈsoʊəs |(also psoas major ) ▶noun Anatomy each of a pair of large muscles that run from the lumbar spine through the groin on either side and, with the iliacus, flex the hip. A second muscle, the psoas minor, has a similar action but is often absent. ORIGIN late 17th cent.: from Greek, accusative plural of psoa, interpreted as singular.
Oxford Dictionary
psoas
psoas |ˈsəʊas |(also psoas major ) ▶noun Anatomy each of a pair of large muscles which run from the lumbar spine through the groin on either side and, with the iliacus, flex the hip. A second muscle, the psoas minor, has a similar action but is often absent. ORIGIN late 17th cent.: from Greek, accusative plural of psoa, interpreted as singular.
The Wordsmith Dictionary