The Collaborative International Dictionary of English v.0.48:

Foehn \Foehn\, n. [G. dial. (Swiss), fr. L. Favonius west wind.
   Cf. Favonian.] (Meteor.)
   (a) A warm dry wind that often blows in the northern valleys
       of the Alps, due to the indraught of a storm center
       passing over Central Europe. The wind, heated by
       compression in its descent from the mountains, reaches
       the base, particularly in winter, dry and warm.
   (b) Any similar wind, as the chinook, in other parts of the
       world.
       [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

foehn
    n 1: a warm dry wind that blows down the northern slopes of the
         Alps [syn: fohn, foehn]