The Collaborative International Dictionary of English v.0.48:

Gibbet \Gib"bet\, n. [OE. gibet, F. gibet, in OF. also club, fr.
   LL. gibetum;; cf. OF. gibe sort of sickle or hook, It.
   giubbetto gibbet, and giubbetta, dim. of giubba mane, also,
   an under waistcoat, doublet, Prov. It. gibba (cf. Jupon);
   so that it perhaps originally signified a halter, a rope
   round the neck of malefactors; or it is, perhaps, derived fr.
   L. gibbus hunched, humped, E. gibbous; or cf. E. jib a sail.]
   [1913 Webster]
   1. A kind of gallows; an upright post with an arm projecting
      from the top, on which, formerly, malefactors were hanged
      in chains, and their bodies allowed to remain as a
      warning.
      [1913 Webster]

   2. The projecting arm of a crane, from which the load is
      suspended; the jib.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Gibbet \Gib"bet\, v. t. [imp. & p. p. Gibbeted; p. pr. & vb.
   n. Gibbeting.]
   [1913 Webster]
   1. To hang and expose on a gibbet.
      [1913 Webster]

   2. To expose to infamy; to blacken.
      [1913 Webster]

            I'll gibbet up his name.              --Oldham.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gibbet
    n 1: alternative terms for gallows [syn: gallows tree,
         gallows-tree, gibbet, gallous]
    v 1: hang on an execution instrument
    2: expose to ridicule or public scorn [syn: pillory, gibbet]