Simple past tense and past participle of blindside.(verb)
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Use "blindsided" in a sentence
"With the help of a demo tactically timed to come out two months before the game, the title blindsided many players who hadn't even heard of it before, but with its for the time awe-inspiring graphics and unusual amount of freedom for a first-person shooter, it quickly won over many fans."
"As I noted here earlier, according to a newsroom source, much of ABC's political team had been "blindsided" by the Breitbart announcenemt, and "not in a good way.""
"Thune told reporters he was "blindsided" by the story, and has made no plans beyond 2010."