[1] : The Collaborative International Dictionary of English v.0.48

grade \grade\ gr=ad, 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
see also:
congress degree gradus at grade down grade up grade 
equating for grades equate grade crossing 

[2] : WordNet (r) 2.0

grade crossing
     n : intersection of a railway and a road on the same level;
         barriers close road when trains pass syn: level
         crossing
see also:
level crossing 

Crossing >> C Words
Crossing, definition of term: Crossing
crossing_pag1.html

Grade >> G Words
Grade, definition of term: Grade
grade_pag1.html

Crossing Over >> C Words
Crossing Over, definition of term: Crossing Over
crossing+over_pag1.html

Grade Separatio >> G Words
Grade Separatio, definition of term: Grade Separatio
grade+separatio_pag1.html

Crossing Guard >> C Words
Crossing Guard, definition of term: Crossing Guard
crossing+guard_pag1.html

Up Grade >> U Words
Up Grade, definition of term: Up Grade
up+grade_pag1.html

Level Crossing >> L Words
Level Crossing, definition of term: Level Crossing
level+crossing_pag1.html