The Collaborative International Dictionary of English v.0.48:

Communicable \Com*mu"ni*ca*ble\ (k[o^]m*m[=u]"n[i^]*k[.a]*b'l),
   a. [Cf. F. communicable, LL. communicabilis.]
   1. Capable of being communicated, or imparted; as, a
      communicable disease; communicable knowledge.
      [1913 Webster]

   2. Communicative; free-speaking. [Obs.] --B. Jonson. --
      Com*mu"ni*ca*ble*ness, n. -- Com*mu"ni*ca"bly, adv.
      [1913 Webster]

WordNet (r) 3.0 (2006):

communicable
    adj 1: (of disease) capable of being transmitted by infection
           [syn: catching, communicable, contagious,
           contractable, transmissible, transmittable]
    2: readily communicated; "communicable ideas"

Moby Thesaurus II by Grady Ward, 1.0:

64 Moby Thesaurus words for "communicable":
   allowable, assignable, bequeathable, bestowable, catching,
   conductive, consignable, contagious, conveyable, deadly,
   destructive, devisable, endemic, envenomed, epidemial, epidemic,
   epiphytotic, epizootic, expansive, expressable, giveable,
   impartable, infectious, infective, inoculable, interchangeable,
   mailable, malign, malignant, mephitic, metathetic, miasmal,
   miasmatic, miasmic, movable, noxious, pandemic, pestiferous,
   pestilential, poisonous, portable, portative, presentable,
   removable, sporadic, spreading, taking, toxic, toxicant,
   toxiferous, transferable, transfusable, transmissible,
   transmissive, transmittable, transportable, transportative,
   transposable, venenate, veneniferous, venenous, venomous, virulent,
   zymotic