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]