deltoid(n = noun.body) deltoid muscle, musculus deltoideus - a large triangular muscle covering the shoulder joint and serving to abduct and flex and extend and rotate the arm;
is a kind of skeletal muscle, striated muscle
is a part of rotator cuff

   deltoid(s = adj.all) - triangular or suggesting a capital delta, with a point at the apex;

deltoid, adj. & n.
--adj. triangular; like a river delta.
--n. (in full deltoid muscle) a thick triangular muscle covering the shoulder joint and used for raising the arm away from the body.

Etymology:
F delto{iuml}de or mod.L deltoides f. Gk deltoeides (as DELTA, -OID)

deltoid eminence, deltoid leaf, deltoid muscle, deltoid tuberosity