The Collaborative International Dictionary of English v.0.48:

Trustworthy \Trust"wor`thy\, a.
   Worthy of trust or confidence; trusty. --
   Trust"wor`thi*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

trustworthy
    adj 1: worthy of trust or belief; "a trustworthy report"; "an
           experienced and trustworthy traveling companion" [syn:
           trustworthy, trusty] [ant: untrustworthy,
           untrusty]
    2: taking responsibility for one's conduct and obligations;
       "trustworthy public servants"

Moby Thesaurus II by Grady Ward, 1.0:

75 Moby Thesaurus words for "trustworthy":
   accurate, authoritative, believable, calculable, colorable,
   conceivable, convincing, credible, dependable, ethical, exact,
   fail-safe, faithful, faithworthy, fast, fiduciary, firm,
   guaranteed, harmless, honest, honorable, incorruptible, invincible,
   inviolable, invulnerable, loyal, moral, plausible, predictable,
   principled, proven, realistic, reliable, responsible, riskless,
   scrupulous, secure, solid, sound, stable, staunch, steadfast,
   steady, straight, substantial, sure, surefire, tenable, tested,
   to be trusted, tried, tried and true, true, trustable, trusty,
   truthful, undangerous, unexceptionable, unfailing, unfalse,
   unhazardous, unimpeachable, unperfidious, unperilous, unprecarious,
   unquestionable, unrisky, untreacherous, upright, valid, veracious,
   warranteed, well-founded, well-grounded, worthy of faith