The Collaborative International Dictionary of English v.0.48:

Sine \Sine\, n. [LL. sinus a sine, L. sinus bosom, used in
   translating the Ar. jaib, properly, bosom, but probably read
   by mistake (the consonants being the same) for an original
   j[imac]ba sine, from Skr. j[imac]va bowstring, chord of an
   arc, sine.] (Trig.)
      (a) The length of a perpendicular drawn from one extremity
          of an arc of a circle to the diameter drawn through
          the other extremity.
      (b) The perpendicular itself. See Sine of angle, below.
          [1913 Webster]

   Artificial sines, logarithms of the natural sines, or
      logarithmic sines.

   Curve of sines. See Sinusoid.

   Natural sines, the decimals expressing the values of the
      sines, the radius being unity.

   Sine of an angle, in a circle whose radius is unity, the
      sine of the arc that measures the angle; in a right-angled
      triangle, the side opposite the given angle divided by the
      hypotenuse. See Trigonometrical function, under
      Function.

   Versed sine, that part of the diameter between the sine and
      the arc.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Versed \Versed\, a. [L. versus turned, p. p. vertere. See 1st
   Versed.] (Math.)
   Turned.
   [1913 Webster]

   Versed sine. See under Sine, and Illust. of Functions.
      [1913 Webster]