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]

Moby Thesaurus II by Grady Ward, 1.0:

91 Moby Thesaurus words for "immobility":
   a wise passiveness, abidingness, changelessness, constancy,
   contemplation, contemplative life, do-nothing policy,
   do-nothingism, do-nothingness, dormancy, durability, durableness,
   duration, endurance, firmness, fixation, fixedness, fixity,
   frozenness, hardening, hibernation, idleness, immobilization,
   immovability, immovableness, immutability, inaction, inactiveness,
   inactivity, indolence, inertia, inertness, inextricability,
   inflexibility, invariability, invariableness, inveteracy,
   irremovability, laissez-aller, laissez-faire, laissez-faireism,
   lastingness, long standing, lull, meditation, motionlessness,
   neutralism, neutrality, neutralness, noninvolvement,
   nonparticipation, nonresistance, nonviolence,
   nonviolent resistance, pacifism, paralysis, passive resistance,
   passive self-annihilation, passiveness, passivism, passivity,
   permanence, permanency, perpetualness, persistence, persistency,
   policy, procrastination, quiescence, quietism, rigidity, solidity,
   stability, stagnancy, stagnation, standing, standpattism, stasis,
   steadfastness, suspension, torpor, unchangeability, unchangingness,
   underactivity, unmovability, unyieldingness, vegetation,
   vis inertiae, vita contemplativa, waiting game,
   watching and waiting