The Collaborative International Dictionary of English v.0.48:

Shelf \Shelf\, n.; pl. Shelves. [OE. shelfe, schelfe, AS.
   scylfe; akin to G. schelfe, Icel. skj[=a]lf. In senses 2 & 3,
   perhaps a different word (cf. Shelve, v. i.).]
   1. (Arch.) A flat tablet or ledge of any material set
      horizontally at a distance from the floor, to hold objects
      of use or ornament.
      [1913 Webster]

   2. A sand bank in the sea, or a rock, or ledge of rocks,
      rendering the water shallow, and dangerous to ships.
      [1913 Webster]

            On the tawny sands and shelves.       --Milton.
      [1913 Webster]

            On the secret shelves with fury cast. --Dryden.
      [1913 Webster]

   3. (Mining) A stratum lying in a very even manner; a flat,
      projecting layer of rock.
      [1913 Webster]

   4. (Naut.) A piece of timber running the whole length of a
      vessel inside the timberheads. --D. Kemp.
      [1913 Webster]

   To lay on the shelf, to lay aside as unnecessary or
      useless; to dismiss; to discard.
      [1913 Webster]

WordNet (r) 3.0 (2006):

shelf
    n 1: a support that consists of a horizontal surface for holding
         objects
    2: a projecting ridge on a mountain or submerged under water
       [syn: ledge, shelf]

Moby Thesaurus II by Grady Ward, 1.0:

112 Moby Thesaurus words for "shelf":
   archives, armory, arsenal, attic, band, bank, bar, basement, bay,
   beam-end, bed, bedding, belt, bin, bonded warehouse, bookcase, box,
   bunker, buttery, cargo dock, cellar, chest, closet, conservatory,
   coral reef, corbel, couche, course, crate, crib, cupboard, deck,
   depository, depot, dock, drawer, dump, exchequer, flat, floor,
   ford, gallery, glory hole, godown, gradin, gradino, hob, hold,
   hutch, layer, ledge, level, library, locker, lumber room,
   lumberyard, magasin, magazine, mantel, mantelshelf, measures,
   overlayer, overstory, predella, rack, reef, repertory, repository,
   reservoir, retable, rick, sandbank, sandbar, seam, shallow,
   shallows, shoal, shoal water, shoulder, stack, stack room, stage,
   step, stock room, storage, store, storehouse, storeroom, story,
   stratum, substratum, superaltar, superstratum, supply base,
   supply depot, tank, thickness, tidal flats, tier, topsoil,
   treasure house, treasure room, treasury, underlayer, understory,
   understratum, vat, vault, warehouse, wetlands, wine cellar, zone



The Free On-line Dictionary of Computing (30 December 2018):

shelf

   A public library of classes for the Eiffel language.