Source : Webster's Revised Unabridged Dictionary (1913)

Dray \Dray\, n. [AS. dr[ae]ge a dragnet, fr. dragan. ????. See
   {Draw}, and cf. 2d {Drag}, 1st {Dredge}.]
   1. A strong low cart or carriage used for heavy burdens.
      --Addison.

   2. A kind of sledge or sled. --Halliwell.

   {Dray cart}, a dray.

   {Dray horse}, a heavy, strong horse used in drawing a dray.

Source : WordNet®

dray horse
     n : horse adapted for drawing heavy loads [syn: {draft horse}, {draught
         horse}]