The Collaborative International Dictionary of English v.0.48:

Superhuman \Su`per*hu"man\, a.
   Above or beyond what is human; sometimes, divine; as,
   superhuman strength; superhuman wisdom.
   [1913 Webster]

WordNet (r) 3.0 (2006):

superhuman
    adj 1: above or beyond the human or demanding more than human
           power or endurance; "superhuman beings"; "superhuman
           strength"; "soldiers driven mad by superhuman misery"
           [ant: subhuman]

Moby Thesaurus II by Grady Ward, 1.0:

76 Moby Thesaurus words for "superhuman":
   Christlike, Christly, Herculean, Hercules, amazing, arcane, brave,
   celestial, courageous, dangerous, daring, death-defying, demigod,
   divine, eerie, empyrean, esoteric, extramundane, extraordinary,
   extraterrestrial, fabulous, fantastic, fey, godlike, godly,
   heavenly, hero, heroic, hypernormal, hyperphysical, incarnate,
   incarnated, incredible, intercessional, intercessive, legendary,
   made flesh, mediative, mediatory, miraculous, mysterious, numinous,
   occult, otherworldly, phenomenal, preterhuman, preternatural,
   preternormal, pretersensual, propitiative, propitiatory, psychic,
   redemptive, salvational, self-existent, spiritual, superior,
   superman, supermundane, supernatural, supernormal, superphysical,
   supersensible, supersensual, supramundane, supranatural,
   transcendent, transcendental, transmundane, unbelievable, uncanny,
   unearthly, unhuman, unnatural, unworldly, valiant