The Collaborative International Dictionary of English v.0.48:

Immobility \Im`mo*bil"i*ty\, n. [L. immobilitas, fr. immobilis
   immovable; pref. im- not + mobilis movable: cf. F.
   immobilit['e]. See Mobile.]
   The condition or quality of being immobile; fixedness in
   place or state.
   [1913 Webster]

WordNet (r) 3.0 (2006):

immobility
    n 1: remaining in place [syn: stationariness, immobility,
         fixedness]
    2: the quality of not moving [ant: mobility]