An enemy.
"The hostile army marched toward our border without warning."
not belonging to your own country's forces or those of an ally
"hostile naval and air forces"
very unfavorable to life or growth
"a hostile climate"
"an uncongenial atmosphere"
"an uncongenial soil"
"the unfriendly environment at high altitudes"
unsolicited and resisted by the management of the target company (used of attempts to buy or take control of a business)
"hostile takeover"
"hostile tender offer"
"hostile bid"
Not friendly; appropriate to an enemy; showing the disposition of an enemy; showing ill will and malevolence or a desire to thwart and injure.
"The general's hostile glare made it clear he intended to destroy anyone who opposed his plan."
In plain English: Hostile means being unfriendly, aggressive, and ready to fight against someone else.
"The crowd gave the speaker hostile shouts when he arrived at the rally."
Usage: Use hostile to describe someone who is openly unfriendly, aggressive, or actively working against you rather than merely being cold or distant. This word often applies specifically to environments like war zones or situations where there is an explicit intent to harm or obstruct others.
The word hostile comes from the Latin hostis, meaning "enemy," and entered English via Middle French around 1300. It replaced an earlier Old English term that carried a similar sense of enmity.