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]