Source : Webster's Revised Unabridged Dictionary (1913)

Downstream \Down"stream`\, adv.
   Down the stream; as, floating downstream.

Source : WordNet®

downstream
     adj : in the direction of a stream's current [ant: {upstream}]
     adv : away from the source or with the current [syn: {downriver}]
           [ant: {upriver}, {upriver}]

Source : Free On-Line Dictionary of Computing

downstream
     
        {upstream}