The Collaborative International Dictionary of English v.0.48:

Tangent \Tan"gent\, n. [L. tangens, -entis, p. pr. of tangere to
   touch; akin to Gr. ? having seized: cf. F. tangente. Cf.
   Attain, Contaminate, Contingent, Entire, Tact,
   Taste, Tax, v. t.] (Geom.)
   A tangent line curve, or surface; specifically, that portion
   of the straight line tangent to a curve that is between the
   point of tangency and a given line, the given line being, for
   example, the axis of abscissas, or a radius of a circle
   produced. See Trigonometrical function, under Function.
   [1913 Webster]

   Artificial tangent, or Logarithmic tangent, the logarithm
      of the natural tangent of an arc.

   Natural tangent, a decimal expressing the length of the
      tangent of an arc, the radius being reckoned unity.

   Tangent galvanometer (Elec.), a form of galvanometer having
      a circular coil and a short needle, in which the tangent
      of the angle of deflection of the needle is proportional
      to the strength of the current.

   Tangent of an angle, the natural tangent of the arc
      subtending or measuring the angle.

   Tangent of an arc, a right line, as ta, touching the arc of
      a circle at one extremity a, and terminated by a line ct,
      passing from the center through the other extremity o.
      [1913 Webster]