The Collaborative International Dictionary of English v.0.48:

Varicella \Var`i*cel"la\, n. [NL., dim. of LL. variola
   smallpox.] (Med.)
   Chicken pox.
   [1913 Webster]

WordNet (r) 3.0 (2006):

varicella
    n 1: an acute contagious disease caused by herpes varicella
         zoster virus; causes a rash of vesicles on the face and
         body [syn: chickenpox, varicella]