sigma, ătis, n., = σίγμα (the Greek letter sigma; hence, from its more ancient form, C).
I A semicircular couch for reclining at meals, Mart. 10, 48, 6; 14, 87, 2; Lampr. Heliog. 25.—
II A bathing-tub of the same shape, Sid. Ep. 2, 2 med. ; id. Carm. 17, 6.