The Collaborative International Dictionary of English v.0.48:

Oread \O"re*ad\, n. [L. Oreas, -adis, Gr. 'Oreia`s, -a`dos, fr.
   'o`ros mountain: cf. F. or['e]ade.] (Class. Myth.)
   One of the nymphs of mountains and grottoes.
   [1913 Webster]

         Like a wood nymph light,
         Oread or Dryad.                          --Milton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Oread
    n 1: (Greek mythology) one of the mountain nymphs