Source : Webster's Revised Unabridged Dictionary (1913)

Whipworm \Whip"worm`\, n. [So called from its shape.] (Zo["o]l.)
   A nematode worm ({Trichocephalus dispar}) often found
   parasitic in the human intestine. Its body is thickened
   posteriorly, but is very long and threadlike anteriorly.