[syn: hostile, uncongenial, unfriendly]
The Collaborative International Dictionary of English v.0.48:
Unfriendly \Un*friend"ly\, a.
   1. Not friendly; not kind or benevolent; hostile; as, an
      unfriendly neighbor.
      [1913 Webster]
   2. Not favorable; not adapted to promote or support any
      object; as, weather unfriendly to health.
      [1913 Webster] -- Un*friend"li*ness, n.
      [1913 Webster]
WordNet (r) 3.0 (2006):
unfriendly
    adj 1: not easy to understand or use; "user-unfriendly" [ant:
           friendly]
    2: not disposed to friendship or friendliness; "an unfriendly
       coldness of manner"; "an unfriendly action to take" [ant:
       friendly]
    3: not friendly; "an unfriendly act of aggression"; "an inimical
       critic" [syn: unfriendly, inimical]
    4: very unfavorable to life or growth; "a hostile climate"; "an
       uncongenial atmosphere"; "an uncongenial soil"; "the
       unfriendly environment at high altitudes" [syn: hostile,
       uncongenial, unfriendly]
Moby Thesaurus II by Grady Ward, 1.0:
132 Moby Thesaurus words for "unfriendly":
   adversary, adversative, adverse, aggressive, alien, allergic,
   antagonistic, anti, antipathetic, antithetic, autistic, averse,
   bashful, battling, bellicose, belligerent, bloodthirsty, bloody,
   bloody-minded, chauvinist, chauvinistic, chill, chilly, clashing,
   close, closed, cold, combative, competitive, con, conflicting,
   contentious, contradictory, contrary, cool, counter, cross,
   disaccordant, disaffected, disenchanted, disinclined, displeased,
   dissentient, dissociable, enemy, ferocious, fierce, fighting,
   fractious, frosty, full of fight, hawkish, hostile, icy, ill,
   incompatible, inhospitable, inimical, insociable, jingo, jingoish,
   jingoist, jingoistic, martial, militant, militaristic, military,
   mopey, mopish, morose, negative, noncooperative, nongregarious,
   not charmed, obstinate, offensive, opponent, opposed, opposing,
   opposite, oppositional, oppositive, oppugnant, overthwart,
   perverse, pugnacious, put off, quarrelsome, recalcitrant,
   refractory, repugnant, rival, saber-rattling, sanguinary,
   sanguineous, savage, scrappy, self-contained, self-sufficient,
   snug, socially incompatible, soldierlike, soldierly, strained,
   sullen, tense, trigger-happy, truculent, unamiable, unamicable,
   unclubbable, uncommunicative, uncompanionable, uncongenial,
   uncooperative, uncordial, unfavorable, ungenial, ungracious,
   unharmonious, unhospitable, unneighborly, unpacific, unpeaceable,
   unpeaceful, unpropitious, unreceptive, unsociable, unsocial,
   warlike, warmongering, warring