Belonging or appropriate to an enemy; showing the disposition of an enemy; showing ill will and malevolence, or a desire to thwart and injure; occupied by an enemy or enemies; inimical; unfriendly; as, a hostile force; hostile intentions; a hostile country; hostile to a sudden change.
very unfavorable to life or growth; "a hostile climate"; "an uncongenial atmosphere"; "an uncongenial soil"; "the unfriendly environment at high altitudes"
Refers to a player of the enemy team, AWACS to planes: "Contact, bullseye 0-7-6, 23, hostile" (enemy player direction 76 degrees, 23 miles from target)
Often refers to an unsolicitated and unwanted bid by the target company. It rejects this bid and indicates that the company does not want to be acquired by that bidder.