Source : Webster's Revised Unabridged Dictionary (1913)

Pumpkin \Pump"kin\, n. [For older pompion, pompon, OF. pompon,
   L. pepo, peponis, Gr. ?, properly, cooked by the sun, ripe,
   mellow; -- so called because not eaten till ripe. Cf. {Cook},
   n.] (Bot.)
   A well-known trailing plant ({Cucurbita pepo}) and its fruit,
   -- used for cooking and for feeding stock; a pompion.

   {Pumpkin seed}.
   (a) The flattish oval seed of the pumpkin.
   (b) (Zo["o]l.) The common pondfish.

Source : WordNet®

pumpkin
     n 1: a coarse vine widely cultivated for its non-keeping large
          pulpy round orange fruit with firm orange skin and
          numerous seeds; subspecies of Cucurbita pepo include the
          summer squashes and a few autumn squashes [syn: {pumpkin
          vine}, {autumn pumpkin}, {Cucurbita pepo}]
     2: usually large pulpy deep-yellow round fruit of the squash
        family maturing in late summer or early autumn

Source : Free On-Line Dictionary of Computing

pumpkin
     
         A humourous term for the {token} - the object
        (notional or real) that gives its possessor (the "pumpking" or
        the "pumpkineer") exclusive access to something, e.g. applying
        {patches} to a master copy of {source} (for which the pumpkin
        is called a "patch pumpkin").
     
        Chip Salzenberg  wrote:
     
        David Croy once told me once that at a previous job, there was
        one tape drive and multiple systems that used it for backups.
        But instead of some high-tech exclusion software, they used a
        low-tech method to prevent multiple simultaneous backups: a
        stuffed pumpkin.  No one was allowed to make backups unless
        they had the "backup pumpkin".
     
        (1999-02-23)