The Collaborative International Dictionary of English v.0.48:

Ledge \Ledge\ (l[e^]j), n. [Akin to AS. licgan to lie, Icel.
   liggja; cf. Icel. l["o]gg the ledge or rim at the bottom of a
   cask. See Lie to be prostrate.] [Formerly written lidge.]
   1. A shelf on which articles may be laid; also, that which
      resembles such a shelf in form or use, as a projecting
      ridge or part, or a molding or edge in joinery.
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   2. A shelf, ridge, or reef, of rocks.
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   3. A layer or stratum.
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            The lowest ledge or row should be of stone. --Sir H.
                                                  Wotton.
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   4. (Mining) A lode; a limited mass of rock bearing valuable
      mineral.
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   5. (Shipbuilding) A piece of timber to support the deck,
      placed athwartship between beams.
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WordNet (r) 3.0 (2006):

ledge
    n 1: a projecting ridge on a mountain or submerged under water
         [syn: ledge, shelf]