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"