The Collaborative International Dictionary of English v.0.48:

Down-wind \Down"-wind`\, adv.
   With the wind.
   [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

downwind \down"wind\ adj.
   on the side or in the direction away from the direction from
   which the wind is blowing; in the direction toward which the
   wind is blowing; as, good hunters stay downwind of their
   prey. Opposite of upwind, and windward.

   Syn: lee(prenominal), leeward.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

downwind
    adv 1: with the wind; in the direction the wind is blowing;
           "they flew downwind" [ant: against the wind, into the
           wind, upwind]
    2: away from the wind; "they were sailing windward" [syn:
       windward, downwind] [ant: leeward, upwind]
    adj 1: towards the side away from the wind [syn: downwind,
           lee(a)]