The Collaborative International Dictionary of English v.0.48:

Herpes \Her"pes\, n. [L., fr. Gr. "e`rphs, fr. "e`rpein to
   creep.] (Med.)
   An eruption of the skin, taking various names, according to
   its form, or the part affected, caused by a herpesvirus
   infection; especially, an eruption of vesicles in small
   distinct clusters, accompanied with itching or tingling,
   including shingles, ringworm, and the like; -- so called from
   its tendency to creep or spread from one part of the skin to
   another.
   [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

herpes
    n 1: viral diseases causing eruptions of the skin or mucous
         membrane
    2: any of the animal viruses that cause painful blisters on the
       skin [syn: herpes, herpes virus]