The Collaborative International Dictionary of English v.0.48:

Rib \Rib\, n. [AS. rib, ribb; akin to D. rib, G. rippe, OHG.
   rippa, rippi, Dan. ribbe, Icel. rif, Russ. rebro.]
   1. (Anat.) One of the curved bones attached to the vertebral
      column and supporting the lateral walls of the thorax.
      [1913 Webster]

   Note: In man there are twelve ribs on each side, of which the
         upper seven are directly connected with the sternum by
         cartilages, and are called sternal, or true, ribs. The
         remaining five pairs are called asternal, or false,
         ribs, and of these each of the three upper pairs is
         attached to the cartilage of the rib above, while the
         two lower pairs are free at the ventral ends, and are
         called floating ribs. See Thorax.
         [1913 Webster]

   2. That which resembles a rib in form or use. Specifically:
      (a) (Shipbuilding) One of the timbers, or bars of iron or
          steel, that branch outward and upward from the keel,
          to support the skin or planking, and give shape and
          strength to the vessel.
      (b) (Mach. & Structures) A ridge, fin, or wing, as on a
          plate, cylinder, beam, etc., to strengthen or stiffen
          it.
      (c) One of the rods on which the cover of an umbrella is
          extended.
      (d) A prominent line or ridge, as in cloth.
      (e) A longitudinal strip of metal uniting the barrels of a
          double-barreled gun.
          [1913 Webster]

   3. (Bot.) The chief nerve, or one of the chief nerves, of a
      leaf.
      (b) Any longitudinal ridge in a plant.
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   4. (Arch.)
      (a) In Gothic vaulting, one of the primary members of the
          vault. These are strong arches, meeting and crossing
          one another, dividing the whole space into triangles,
          which are then filled by vaulted construction of
          lighter material. Hence, an imitation of one of these
          in wood, plaster, or the like.
      (b) A projecting mold, or group of moldings, forming with
          others a pattern, as on a ceiling, ornamental door, or
          the like.
          [1913 Webster]

   5. (Mining)
      (a) Solid coal on the side of a gallery; solid ore in a
          vein.
      (b) An elongated pillar of ore or coal left as a support.
          --Raymond.
          [1913 Webster]

   6. A wife; -- in allusion to Eve, as made out of Adam's rib.
      [Familiar & Sportive]
      [1913 Webster]

            How many have we known whose heads have been broken
            with their own rib.                   --Bp. Hall.
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   Chuck rib, a cut of beef immediately in front of the middle
      rib. See Chuck.

   Fore ribs, a cut of beef immediately in front of the
      sirloin.

   Middle rib, a cut of beef between the chuck rib and the
      fore ribs.

   Rib grass. (Bot.) Same as Ribwort.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rib \Rib\, v. t. [imp. & p. p. Ribbed; p. pr. & vb. n.
   Ribbing.]
   1. To furnish with ribs; to form with rising lines and
      channels; as, to rib cloth.
      [1913 Webster]

   2. To inclose, as with ribs, and protect; to shut in.
      [1913 Webster]
      [1913 Webster]

            It [lead] were too gross
            To rib her cerecloth in the obscure grave. --Shak.
      [1913 Webster]

   To rib land, to leave strips of undisturbed ground between
      the furrows in plowing.
      [1913 Webster]

WordNet (r) 3.0 (2006):

rib
    n 1: support resembling the rib of an animal
    2: any of the 12 pairs of curved arches of bone extending from
       the spine to or toward the sternum in humans (and similar
       bones in most vertebrates) [syn: rib, costa]
    3: cut of meat including one or more ribs
    4: a teasing remark
    5: a riblike supporting or strengthening part of an animal or
       plant
    6: a projecting molding on the underside of a vault or ceiling;
       may be ornamental or structural
    v 1: form vertical ribs by knitting; "A ribbed sweater"
    2: subject to laughter or ridicule; "The satirists ridiculed the
       plans for a new opera house"; "The students poked fun at the
       inexperienced teacher"; "His former students roasted the
       professor at his 60th birthday" [syn: ridicule, roast,
       guy, blackguard, laugh at, jest at, rib, make
       fun, poke fun]

Moby Thesaurus II by Grady Ward, 1.0:

128 Moby Thesaurus words for "rib":
   Chateaubriand, banter, better half, bilge, blade roast, blain,
   bleb, blister, blob, boss, bow, breast, brisket, bubble, bulb,
   bulge, bulla, bump, bunch, burl, button, cahot, chaff, chine,
   chuck, chuck roast, clod, clump, cold cuts, common-law wife,
   concubine, condyle, convex, dowel, ear, feme, feme covert,
   filet mignon, flange, flank, flap, fool, fun, gall, gnarl,
   goodwife, goody, handle, haze, helpmate, helpmeet, hill, hump,
   hunch, jape, jest, jive, jog, joggle, joke, jolly, josh, kid, knob,
   knot, knuckle, knur, knurl, lady, lip, loin, loop, lump,
   married woman, matron, mole, mountain, needle, nevus, nub, nubbin,
   nubble, old lady, old woman, papilloma, peg, plate, plate piece,
   pot roast, put on, rack, rag, rally, razz, rib roast, ribs, ride,
   ridge, ring, roast, rolled roast, round, rump, rump roast, saddle,
   shank, short ribs, shoulder, shoulder clod, sirloin, spine, squaw,
   stud, style, tab, tease, tenderloin, tubercle, tubercule, twit,
   verruca, vesicle, wale, wart, wedded wife, welt, wife, woman