The Collaborative International Dictionary of English v.0.48:

Gradient \Gra"di*ent\, a. [L. gradiens, p. pr. of gradi to step,
   to go. See Grade.]
   1. Moving by steps; walking; as, gradient automata.
      --Wilkins.
      [1913 Webster]

   2. Rising or descending by regular degrees of inclination;
      as, the gradient line of a railroad.
      [1913 Webster]

   3. Adapted for walking, as the feet of certain birds.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Gradient \Gra"di*ent\, n.
   1. The rate of regular or graded ascent or descent in a road;
      grade.
      [1913 Webster]

   2. A part of a road which slopes upward or downward; a
      portion of a way not level; a grade.
      [1913 Webster]

   3. The rate of increase or decrease of a variable magnitude,
      or the curve which represents it; as, a thermometric
      gradient.

   4. (Chem., Biochem.) The variation of the concentration of a
      chemical substance in solution through some linear path;
      also called concentration gradient; -- usually measured in
      concentration units per unit distance. Concentration
      gradients are created naturally, e.g. by the diffusion of
      a substance from a point of high concentration toward
      regions of lower concentration within a body of liquid; in
      laboratory techniques they may be made artificially.
      [PJC]

   gradient maker (Biochem.) a device which creates a
      concentration gradient in a solution within some
      apparatus; -- used, e. g., for separation of biochemical
      substances.
      [PJC]

   Gradient post, a post or stake indicating by its height or
      by marks on it the grade of a railroad, highway, or
      embankment, etc., at that spot. Gradin

The Collaborative International Dictionary of English v.0.48:

del \del\ n. (Math.)
   a differential operator which, operating on a function of
   several variables, gives the sum of the partial derivatives
   of the function with respect to the three orthogonal spatial
   coordinates; -- also called the gradient or grad. It is
   represented by an inverted Greek capital delta ([nabla]), and
   is thus because of its shape also called nabla, meaning
   harp in Hebrew.
   [PJC]

WordNet (r) 3.0 (2006):

gradient
    n 1: a graded change in the magnitude of some physical quantity
         or dimension
    2: the property possessed by a line or surface that departs from
       the horizontal; "a five-degree gradient" [syn: gradient,
       slope]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "gradient":
   bank, bevel, bezel, chute, easy slope, fleam, gentle slope, glacis,
   grade, hanging gardens, helicline, hillside, inclination, incline,
   inclined plane, launching ramp, lean, leaning, pitch, ramp, rise,
   rising, scarp, shelving beach, side, slant, slope, steep slope,
   stiff climb, talus, tilt, uprise, uprising, vertical height