The Collaborative International Dictionary of English v.0.48:

Latency \La"ten*cy\, n. [See Latent.]
   1. The state or quality of being latent.
      [1913 Webster]

            To simplify the discussion, I shall distinguish
            three degrees of this latency.        --Sir W.
                                                  Hamilton.
      [1913 Webster]

   2. The time between a stimulus the appearance of the
      response; the time between any causal action and the first
      appearance of the effect. Called also latent period.
      [PJC]

   3. Hence: (Med.) The time between exposure to a carcinogen or
      other disease-causing agent and the appearance of the
      consequent disease.
      [PJC]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "latency":
   abeyance, apathy, catalepsy, catatonia, cold storage, deadliness,
   deathliness, delitescence, doldrums, dormancy, entropy,
   indifference, indolence, inertia, inertness, intermission,
   interruption, languor, latent content, latent meaningfulness,
   latentness, lotus-eating, passiveness, passivity, possibility,
   potentiality, quiescence, quiescency, stagnancy, stagnation,
   stasis, suspense, suspension, torpor, vegetation, virtuality,
   vis inertiae