The Collaborative International Dictionary of English v.0.48:

Trusty \Trust"y\, a. [Compar. Trustier; superl. Trustiest.]
   1. Admitting of being safely trusted; justly deserving
      confidence; fit to be confided in; trustworthy; reliable.
      [1913 Webster]

            Your trusty and most valiant servitor. --Shak.
      [1913 Webster]

   2. Hence, not liable to fail; strong; firm.
      [1913 Webster]

            His trusty sword he called to his aid. --Spenser.
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   3. Involving trust; as, a trusty business. [R.] --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

trusty
    adj 1: worthy of trust or belief; "a trustworthy report"; "an
           experienced and trustworthy traveling companion" [syn:
           trustworthy, trusty] [ant: untrustworthy,
           untrusty]
    n 1: a convict who is considered trustworthy and granted special
         privileges

Moby Thesaurus II by Grady Ward, 1.0:

96 Moby Thesaurus words for "trusty":
   POW, believable, cageling, calculable, captive, chain gang,
   childlike, colorable, con, conceivable, confiding, convict,
   credible, credulous, dependable, dependent, depending, detenu,
   ex-convict, faithful, faithworthy, fast, fiduciary, firm,
   galantuomo, gaolbird, gentilhomme, gentleman, good man, good woman,
   guileless, honest man, honest woman, incorruptible, innocent,
   internee, invincible, inviolable, jailbird, lady, lifer,
   man of honor, naive, parolee, plausible, political prisoner,
   predictable, prisoner, prisoner of war, proven, real lady,
   reliable, reliant, relying, responsible, secure, solid, sound,
   stable, staunch, steadfast, steady, stir bird, straight,
   straight shooter, substantial, sure, surefire, tenable, tested,
   ticket-of-leave man, ticket-of-leaver, to be trusted, tried,
   tried and true, true, true blue, truepenny, trustable, trustful,
   trusting, trustworthy, unexceptionable, unfailing, unfalse,
   unimpeachable, unperfidious, unquestionable, unsuspecting,
   unsuspicious, untreacherous, well-founded, well-grounded,
   without suspicion, woman of honor, worthy of faith