The Collaborative International Dictionary of English v.0.48:

Pox \Pox\, n. [For pocks, OE. pokkes. See Pock. It is plural
   in form but is used as a singular.] (Med.)
   Strictly, a disease by pustules or eruptions of any kind, but
   chiefly or wholly restricted to three or four diseases, --
   the smallpox, the chicken pox, and the vaccine and the
   venereal diseases.
   [1913 Webster]

   Note: Pox, when used without an epithet, as in imprecations,
         formerly signified smallpox; but it now signifies
         syphilis.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pox \Pox\, v. t. [imp. & p. p. Poxed; p. pr. & vb. n.
   Poxing.]
   To infect with the pox, or syphilis.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pox
    n 1: a common venereal disease caused by the treponema pallidum
         spirochete; symptoms change through progressive stages; can
         be congenital (transmitted through the placenta) [syn:
         syphilis, syph, pox, lues venerea, lues]
    2: a contagious disease characterized by purulent skin eruptions
       that may leave pock marks

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "pox":
   French disease, Spanish pox, VD, acquired syphilis,
   balanitis gangrenosa, cerebral tabes, chancre, chancroid, clap,
   claps, climatic bubo, congenital syphilis, constitutional syphilis,
   dose, dose of clap, fifth venereal disease, general paresis,
   gonorrhea, granuloma inguinale, granuloma venereum, great pox,
   hard chancre, latent syphilis, locomotor ataxia, morbus Gallicus,
   paralytic dementia, paresis, pudendal ulcer, simple chancre,
   social disease, soft chancre, syph, syphilis,
   syphilitic meningoencephalitis, tabes, tabes dorsales,
   tertiary syphilis, tropical bubo, venereal disease