Source : Webster's Revised Unabridged Dictionary (1913)

Cottontail \Cot"ton*tail`\ (k[o^]t"t'n*t[=a]l`), n. (Zo["o]l.)
   The American wood rabbit ({Lepus sylvaticus}); -- also called
   {Molly cottontail}.

Source : WordNet®

cottontail
     n : common small rabbit of North America having grayish or
         brownish fur and a tail with a white underside; a host
         for Ixodes pacificus and Ixodes scapularis (Lyme disease
         ticks) [syn: {wood rabbit}, {cottontail rabbit}]