The Collaborative International Dictionary of English v.0.48:

Grade \Grade\, v. t. [imp. & p. p. Graded; p. pr. & vb. n.
   Grading.]
   1. To arrange in order, steps, or degrees, according to size,
      quality, rank, etc.
      [1913 Webster]

   2. To reduce to a level, or to an evenly progressive ascent,
      as the line of a canal or road.
      [1913 Webster]

   3. (Stock Breeding) To cross with some better breed; to
      improve the blood of.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Grade \Grade\ (gr[=a]d), n. [F. grade, L. gradus step, pace,
   grade, from gradi to step, go. Cf. Congress, Degree,
   Gradus.]
   1. A step or degree in any series, rank, quality, order;
      relative position or standing; as, grades of military
      rank; crimes of every grade; grades of flour.
      [1913 Webster]

            They also appointed and removed, at their own
            pleasure,
            teachers of every grade.              --Buckle.
      [1913 Webster]

   2. In a railroad or highway:
      (a) The rate of ascent or descent; gradient; deviation
          from a level surface to an inclined plane; -- usually
          stated as so many feet per mile, or as one foot rise
          or fall in so many of horizontal distance; as, a heavy
          grade; a grade of twenty feet per mile, or of 1 in
          264.
      (b) A graded ascending, descending, or level portion of a
          road; a gradient.
          [1913 Webster]

   3. (Stock Breeding) The result of crossing a native stock
      with some better breed. If the crossbreed have more than
      three fourths of the better blood, it is called high
      grade.
      [1913 Webster]

   At grade, on the same level; -- said of the crossing of a
      railroad with another railroad or a highway, when they are
      on the same level at the point of crossing.

   Down grade, a descent, as on a graded railroad.

   Up grade, an ascent, as on a graded railroad.

   Equating for grades. See under Equate.

   Grade crossing, a crossing at grade.
      [1913 Webster]

WordNet (r) 3.0 (2006):

grade
    n 1: a body of students who are taught together; "early morning
         classes are always sleepy" [syn: class, form, grade,
         course]
    2: a relative position or degree of value in a graded group;
       "lumber of the highest grade" [syn: grade, level, tier]
    3: the gradient of a slope or road or other surface; "the road
       had a steep grade"
    4: one-hundredth of a right angle [syn: grad, grade]
    5: a degree of ablaut [syn: grade, gradation]
    6: a number or letter indicating quality (especially of a
       student's performance); "she made good marks in algebra";
       "grade A milk"; "what was your score on your homework?" [syn:
       mark, grade, score]
    7: the height of the ground on which something stands; "the base
       of the tower was below grade" [syn: grade, ground level]
    8: a position on a scale of intensity or amount or quality; "a
       moderate grade of intelligence"; "a high level of care is
       required"; "it is all a matter of degree" [syn: degree,
       grade, level]
    9: a variety of cattle produced by crossbreeding with a superior
       breed
    v 1: assign a rank or rating to; "how would you rank these
         students?"; "The restaurant is rated highly in the food
         guide" [syn: rate, rank, range, order, grade,
         place]
    2: level to the right gradient
    3: assign a grade or rank to, according to one's evaluation;
       "grade tests"; "score the SAT essays"; "mark homework" [syn:
       grade, score, mark]
    4: determine the grade of or assign a grade to

Moby Thesaurus II by Grady Ward, 1.0:

258 Moby Thesaurus words for "grade":
   acclivity, adjust, align, alphabetize, amount, analyze, arrange,
   array, ascend, ascent, assort, bank, bevel, bezel, blood, bolt,
   bracket, branch, break down, bulk, caliber, calibrate, calibrated,
   cant, careen, caste, catalog, categorize, category, chute, clan,
   class, classify, climb, codify, collate, compass, condition,
   cool off, correct, cut, cut it, dab, decline, declivity, decrease,
   degree, deploy, descend, descent, differentiate, digest, dip,
   dispose, divide, division, downgrade, drag, dress, drop, dub,
   easy slope, echelon, enlarge, equalize, estate, evaluate, even,
   extent, fall, fall away, fall off, fell, file, flatten, fleam,
   flush, form, gauge, gentle slope, glacis, go downhill, go uphill,
   gradate, gradation, gradational, gradient, gradual, graduate,
   graduated, grease, group, grouping, hack it, hanging gardens,
   harmonize, harrow, head, heading, height, helicline, hierarchic,
   hierarchize, hill, hillside, inclination, incline, inclined plane,
   increase, index, interval, keel, kin, label, launching ramp, lay,
   lay down, lay flat, lay level, lay low, lay out, league, lean,
   leaning, leap, level, line up, list, lubricate, make it,
   make the grade, mark, marshal, match, measure, measure up,
   methodize, mow, normalize, notch, nuance, oil, order, organize,
   pacify, pas, pass, peg, period, pigeonhole, pitch, place, plane,
   planish, plaster, plateau, point, position, predicament,
   progressive, proportion, qualify, quiet, race, rake, ramp, range,
   rank, rase, rate, rating, ratio, raze, reach, regular, regularize,
   regulate, remove, retreat, riddle, rise, roll, roll flat, round,
   routinize, rubric, rung, scalar, scale, scarp, scope, score,
   screen, section, separate, sept, set, set up, shade, shade off,
   shadow, shave, shelve, shelving beach, side, sidle, sieve, sift,
   situation, size, slant, slope, smooth, smooth down, smooth out,
   smoothen, sort, sort out, space, stage, stair, standard,
   standardize, standing, state, station, status, steamroll,
   steamroller, steep slope, step, stiff climb, stint, strain,
   stratum, structure, subdivide, subdivision, subgroup, suborder,
   subordinate, succeed, swag, sway, systematize, tabulate, talus,
   tier, tilt, tip, title, track, tranquilize, tread, type, upgrade,
   uprise, year