The Collaborative International Dictionary of English v.0.48:

Detrimental \Det`ri*men"tal\, a.
   Causing detriment; injurious; hurtful.
   [1913 Webster]

         Neither dangerous nor detrimental to the donor.
                                                  --Addison.

   Syn: Injurious; hurtful; prejudicial; disadvantageous;
        mischievous; pernicious.
        [1913 Webster]

WordNet (r) 3.0 (2006):

detrimental
    adj 1: (sometimes followed by `to') causing harm or injury;
           "damaging to career and reputation"; "the reporter's
           coverage resulted in prejudicial publicity for the
           defendant" [syn: damaging, detrimental,
           prejudicial, prejudicious]

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "detrimental":
   adverse, antagonistic, bad, baleful, baneful, conflicting,
   contrary, corroding, corrosive, corrupting, corruptive, counter,
   counteractive, counterproductive, damaging, deadly, deleterious,
   destructive, difficult, disadvantageous, disserviceable,
   distressing, evil, hard, harmful, hostile, hurtful, ill,
   in opposition, inimical, injurious, lethal, malefic, malevolent,
   malign, malignant, mischievous, miserable, negative, noisome,
   not easy, noxious, ominous, opposed, opposing, opposite,
   pernicious, poisonous, prejudicial, rigorous, scatheful, sinister,
   stressful, toxic, troublesome, troublous, trying, unadvantageous,
   unfavorable, unprofitable, unrewarding, untoward, useless,
   venenate, veneniferous, venenous, venomous, vicious, virulent,
   worthless, wretched