The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

   Pumpkin seed.
   (a) The flattish oval seed of the pumpkin.
   (b) (Zool.) The common pondfish.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

crookneck \crook"neck`\, n.
   Either of two varieties of squash, distinguished by their
   tapering, recurved necks. The summer crookneck is
   botanically a variety of the pumpkin (Cucurbita pepo) and
   matures early in the season. It is pale yellow in color, with
   warty excrescences. The winter crookneck belongs to a
   distinct species (Cucurbita moschata) and is smooth and
   often striped. [U. S.]

   Syn: crookneck squash.
        [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

Cucurbita pepo
    n 1: a coarse vine widely cultivated for its 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, pumpkin vine,
         autumn pumpkin, Cucurbita pepo]