Definitions of unfriendly:

• adjective:   not friendly

  Example: "An unfriendly act of aggression"

• adjective:   not disposed to friendship or friendliness

  Example: "An unfriendly coldness of manner"

• adjective:   not easy to understand or use

  Example: "User-unfriendly"

• adjective:   lacking warmth of feeling

  Example: "An unfriendly manner"

• adjective:   very unfavorable to life or growth

  Example: "The unfriendly environment at high altitudes"