Source : Webster's Revised Unabridged Dictionary (1913)

Grade \Grade\, 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.

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

   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.

   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.

   {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.

Source : WordNet®

grade crossing
     n : intersection of a railway and a road on the same level;
         barriers close road when trains pass [syn: {level
         crossing}]