The phrase "decidedly hostile" is correct and can be used in written English.
It means strongly or definitely hostile, indicating a clear and unyielding negative attitude or animosity. Example: "The negotiations between the two countries were met with a decidedly hostile response from the opposing side, making it difficult to reach a compromise."
First Union and SunTrust Banks are waging a decidedly hostile advertising campaign to sway Wachovia's shareholders in a coming proxy vote.
The collective governance that the E.U. sorely needs to thrive in a globalized world is at odds with a political street that is becoming decidedly hostile to the European project.
Randy advances to the microphone with the swaggering stage presence of P.T. Barnum and tries to crack a few jokes that get greeted with jeers and catcalls from the decidedly hostile audience.
China is open to foreign investment but is decidedly hostile to uncontrolled, nongovernment information and news.
Barcelona will face a decidedly hostile atmosphere inside the Bernabeu, with only 500 of their supporters tucked away in a corner high inside the grand old stadium.
Trump marched into decidedly hostile territory on a trip that puzzled and infuriated Mexicans across political lines.
While that is true, the right has been decidedly more hostile to Mr. Simpson.
But some of the banks were working on a decidedly more hostile presentation: the unsolicited $44.5 billion takeover offer by Comcast for AT&T's cable business, AT&T Broadband.
So the mood at Mr. Slimane's spring showing on Monday night was decidedly less hostile, both from the perspective of the audience and, it would appear, that of the designer, for the main reason that, by most accounts, the clothes are selling.
That was decidedly unfriendly.
What those Membership First officers were trying to do in 2008, despite a decidedly labor-hostile environment, was provide SAG membership with the best contract they could possibly deliver.
