Simple past tense and past participle of double-check.(verb)
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Use "double-checked" in a sentence
"He does make it clear the quotes are from the finished text but unfortunately leaves it vague as to whether he read that text or simply double-checked it for the quotes."
"He double-checked that his car was locked, then headed down towards the river, turning his thoughts to the meeting he was due to attend—a pre-trial briefing at the Four Courts with the state prosecutor."
"When I told him, Mr. Soper double-checked, frustration wrinkling his brow."