The Collaborative International Dictionary of English v.0.48:

Immediacy \Im*me"di*a*cy\, n.
   The relation of freedom from the interventionof a medium;
   immediateness. --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

immediacy
    n 1: lack of an intervening or mediating agency; "the immediacy
         of television coverage" [syn: immediacy, immediateness]
         [ant: mediacy, mediateness]
    2: immediate intuitive awareness [syn: immediacy, immediate
       apprehension]
    3: the quickness of action or occurrence; "the immediacy of
       their response"; "the instancy of modern communication" [syn:
       immediacy, immediateness, instantaneousness,
       instancy]

Moby Thesaurus II by Grady Ward, 1.0:

69 Moby Thesaurus words for "immediacy":
   accessibility, actual presence, alacrity, approach, approximation,
   availability, being here, being there, case of need, closeness,
   confines, contiguity, contiguousness, convergence, decisiveness,
   dire necessity, dispatch, environs, exigence, exigency, existence,
   expedition, expeditiousness, foreground, hereness, immanence,
   immediate foreground, immediateness, imperative, imperativeness,
   indwellingness, inherence, instantaneity, instantaneousness,
   matter of necessity, momentaneousness, momentariness, nearness,
   neighborhood, nighness, occurrence, physical presence, precinct,
   predicament, presence, pressingness, pressure, promptitude,
   promptness, propinquity, proximity, punctuality, punctualness,
   purlieus, quickness, rapidity, readiness, simultaneity, speediness,
   spiritual presence, summariness, swiftness, thereness, ubiety,
   urgency, urgent need, vicinage, vicinity, whereness