The Collaborative International Dictionary of English v.0.48:

Subsidence \Sub*sid"ence\, Subsidency \Sub*sid"en*cy\, n. [L.
   subsidens, -entis, p. pr. of subsidere. See Subside.]
   The act or process of subsiding.
   [1913 Webster]

         The subdual or subsidence of the more violent passions.
                                                  --Bp.
                                                  Warburton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

subsidence
    n 1: an abatement in intensity or degree (as in the
         manifestations of a disease); "his cancer is in remission"
         [syn: remission, remittal, subsidence]
    2: a gradual sinking to a lower level [syn: settling,
       subsiding, subsidence]
    3: the sudden collapse of something into a hollow beneath it
       [syn: cave in, subsidence]