The Collaborative International Dictionary of English v.0.48:

Prominent \Prom"i*nent\, a. [L. prominens, -entis, p. pr. of
   prominere to jut out, to project; pro before, forward +
   minere (in comp.) to jut, project: cf. F. prominent. See
   Imminent, Eminent.]
   [1913 Webster]
   1. Standing out, or projecting, beyond the line surface of
      something; jutting; protuberant; in high relief; as, a
      prominent figure on a vase.
      [1913 Webster]

   2. Hence; Distinctly manifest; likely to attract attention
      from its size or position; conspicuous; as, a prominent
      feature of the face; a prominent building.
      [1913 Webster]

   3. Eminent; distinguished above others; as, a prominent
      character.
      [1913 Webster]

   Prominent' moth (Zool.), any moth of the family
      Notodontid[ae]; a notodontian; -- so called because the
      larva has a hump or prominence on its back. Several of the
      species are injurious to fruit trees.
      [1913 Webster]

WordNet (r) 3.0 (2006):

prominent
    adj 1: having a quality that thrusts itself into attention; "an
           outstanding fact of our time is that nations poisoned by
           anti semitism proved less fortunate in regard to their
           own freedom"; "a new theory is the most prominent feature
           of the book"; "salient traits"; "a spectacular rise in
           prices"; "a striking thing about Picadilly Circus is the
           statue of Eros in the center"; "a striking resemblance
           between parent and child" [syn: outstanding,
           prominent, salient, spectacular, striking]
    2: conspicuous in position or importance; "a big figure in the
       movement"; "big man on campus"; "he's very large in financial
       circles"; "a prominent citizen" [syn: big, large,
       prominent]