Source : Webster's Revised Unabridged Dictionary (1913)

Unfriendly \Un*friend"ly\, a.
   1. Not friendly; not kind or benevolent; hostile; as, an
      unfriendly neighbor.

   2. Not favorable; not adapted to promote or support any
      object; as, weather unfriendly to health. --
      {Un*friend"li*ness}, n.

Source : WordNet®

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: lacking warmth of feeling; "a chilly greeting"; "an
        unfriendly manner" [syn: {chilly}]
     4: not friendly; "an unfriendly act of aggression"; "an
        inimical critic" [syn: {inimical}]
     5: very unfavorable to life or growth; "a hostile climate"; "an
        uncongenial atmosphere"; "an uncongenial soil"; "the
        unfriendly environment at high altitudes" [syn: {hostile},
         {uncongenial}]
     [also: {unfriendliest}, {unfriendlier}]