unshakable

from WordNet (r) 3.0 (2006)

unshakable
    adj 1: marked by firm determination or resolution; not shakable;
           "firm convictions"; "a firm mouth"; "steadfast resolve";
           "a man of unbendable perseverence"; "unwavering loyalty"
           [syn: {firm}, {steadfast}, {steady}, {stiff},
           {unbendable}, {unfaltering}, {unshakable}, {unwavering}]
    2: without flaws or loopholes; "an ironclad contract"; "a
       watertight alibi"; "a bulletproof argument" [syn:
       {unassailable}, {unshakable}, {watertight}, {bulletproof}]

from The Collaborative International Dictionary of English v.0.48

Unshakable \Un*shak"a*ble\, a.
   Not capable of being shaken; firm; fixed. --Shak. J. S. Mill.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

24 Moby Thesaurus words for "unshakable":
      abiding, balanced, cool, fast, fiducial, firm, firm as Gibraltar,
      fixed, imperturbable, in equilibrium, predictable, reliable,
      secure, solid, sound, stable, steadfast, steady, substantial,
      unflappable, unflinching, unwavering, well-balanced,
      without nerves

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