\Lit"u*us\, n.; pl. {Litui}. [L.]
1. (Rom. Antig.)
   (a) A curved staff used by the augurs in quartering the
       heavens.
   (b) An instrument of martial music; a kind of trumpet of a
       somewhat curved form and shrill note.
2. (Math.) A spiral whose polar equation is r^{2}[theta] = 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.