资料来源 : Webster's Revised Unabridged Dictionary (1913)

Lituus \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.