The Collaborative International Dictionary of English v.0.48:

acne \ac"ne\ ([a^]k"n[-e]), n. [NL., prob. a corruption of Gr.
   'akmh`.] (Med.)
   Inflammation of the sebaceous glands that are associated with
   hair follicles, leading to visible comedones and pimples,
   especially on the face, back, and chest.
   [1913 Webster + AS]

WordNet (r) 3.0 (2006):

acne
    n 1: an inflammatory disease involving the sebaceous glands of
         the skin; characterized by papules or pustules or comedones

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "acne":
   acne vulgaris, dermamycosis, dermatitis, dermatosis, eczema,
   elephantiasis, epithelioma, erysipelas, erythema, exanthem,
   heat rash, herpes, herpes simplex, herpes zoster, hives, impetigo,
   itch, jungle rot, leprosy, lichen, lichen primus, lupus,
   lupus vulgaris, miliaria, pemphigus, prickly heat, pruigo,
   pruritus, psora, ringworm, scabies, shingles, skin cancer,
   tetter