The Collaborative International Dictionary of English v.0.48:

Immobile \Im*mo"bile\, a. [L. immobilis: cf. F. immobile. See
   Immobility.]
   Incapable of being moved; immovable; fixed; stable. --Prof.
   Shedd.
   [1913 Webster] immobilisation

WordNet (r) 3.0 (2006):

immobile
    adj 1: not capable of movement or of being moved [ant: mobile]
    2: securely fixed in place; "the post was still firm after being
       hit by the car" [syn: fast, firm, immobile]

Moby Thesaurus II by Grady Ward, 1.0:

83 Moby Thesaurus words for "immobile":
   abiding, adamant, adamantine, at a standstill, at anchor,
   changeless, constant, contemplative, continuing, dead-still,
   do-nothing, dormant, durable, enduring, firm, fixed, frozen, idle,
   immotile, immotive, immovable, immutable, inactive, inert,
   inflexible, intact, inviolate, irremovable, laissez-aller,
   laissez-faire, lasting, meditative, motionless, moveless, neuter,
   neutral, out of commission, paralytic, paralyzed, passive, pat,
   permanent, perpetual, persistent, procrastinating, quiescent,
   quietist, quietistic, remaining, riding at anchor, rigid, solid,
   stable, stagnant, stagnating, standpat, static, stationary,
   statuelike, staying, steadfast, still, stock-still, sustained,
   torpid, unaltered, unchangeable, unchanged, unchanging, unchecked,
   undestroyed, unemployed, unfading, unfailing, unmovable, unmoved,
   unmoving, unshifting, unvaried, unvarying, unyielding, vegetable,
   vegetative