Source : Webster's Revised Unabridged Dictionary (1913)

Mountainous \Moun"tain*ous\, a. [F. montagneux, L. montaniosus.]
   1. Full of, or containing, mountains; as, the mountainous
      country of the Swiss.

   2. Inhabiting mountains. [Obs.] --Bacon.

   3. Large as, or resembling, a mountain; huge; of great bulk;
      as, a mountainous heap. --Prior.

Source : WordNet®

mountainous
     adj 1: having hills and crags; "hilly terrain" [syn: {cragged}, {craggy},
             {hilly}]
     2: like a mountain in size and impressiveness; "mountainous
        waves"; "a mountainous dark man"
     3: containing many mountains