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):

summer crookneck
    n 1: yellow squash with a thin curved neck and somewhat warty
         skin [syn: crookneck, crookneck squash, summer
         crookneck]