1. (adj)unfriendly not easy to understand or use
"user-unfriendly"
2. (adj)unfriendly not disposed to friendship or friendliness "an unfriendly coldness of manner"; "an unfriendly action to take"
3. (adj)unfriendly, inimical not friendly "an unfriendly act of aggression"; "an inimical critic"
4. (adj)hostile, uncongenial, unfriendly very unfavorable to life or growth "a hostile climate"; "an uncongenial atmosphere"; "an uncongenial soil"; "the unfriendly environment at high altitudes"