Lituus

·noun A curved staff used by the augurs in quartering the heavens.

II. Lituus ·noun An instrument of martial music; a kind of trumpet of a somewhat curved form and shrill note.

III. Lituus ·noun A spiral whose polar equation is r2 = a; that is, a curve the square of whose radius vector varies inversely as the angle which the radius vector makes with a given line.