Simple past tense and past participle of fester.(verb)
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Use "festered" in a sentence
"Patrick Kennedy holds similar views to his late father, and the dispute with Tobin festered anew when Kennedy publicly criticized the Catholic Church for opposing health care reform that lacked stringent anti-abortion language."
"But as the losses mounted - 1, 2, then 14 straight, the idea festered, and finally, while doing a local broadcast before a Monday night game, Diliberto reached under his chair, grabbed the bag and placed it over his head."
"Frances kind of festered over the -- over Florida."