Definify.com
Webster 1913 Edition
Purpura
‖
1. 
(Med.) 
A disease characterized by livid spots on the skin from extravasated blood, with loss of muscular strength, pain in the limbs, and mental dejection; the purples. 
Dunglison.
 2. 
(Zool.) 
A genus of marine gastropods, usually having a rough and thick shell. Some species yield a purple dye.