The Collaborative International Dictionary of English v.0.48:

Melanoma \Mel`a*no"ma\, n.; L. pl. -nomata. [NL.; Gr. ?, ?,
   black + -oma.] (Med.)
   (a) A tumor containing dark pigment. Such tumors are usually
       malignant and often fatal.
   (b) Development of dark-pigmented tumors.
       [Webster 1913 Suppl. +PJC]