The Collaborative International Dictionary of English v.0.48:

Promontory \Prom"on*to*ry\, n.; pl. Promontories. [ L.
   promonturium, promunturium; pro before + mons, montis,
   mountain: cf. F. promontoire. See Mount, n.]
   [1913 Webster]
   1. (Phys. Geog.) A high point of land or rock projecting into
      the sea beyond the line of coast; a headland; a high cape.
      [1913 Webster]

            Like one that stands upon a promontory. --Shak.
      [1913 Webster]

   2. (Anat.) A projecting part. Especially:
      (a) The projecting angle of the ventral side of the sacrum
          where it joins the last lumbar vertebra.
      (b) A prominence on the inner wall of the tympanum of the
          ear.
          [1913 Webster]