Superlative form of feisty: most feisty.(adjective)
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Use "feistiest" in a sentence
"• Robert Heath called it the "feistiest" advocacy campaign to date."
"Rep. Frank has been in Congress since 1980, and he's been of the feistiest members, having gone toe to toe with numerous of his colleagues and with the media."
"In their feistiest face-off of the race, the four Democrats vying for the US Senate clashed in a radio debate yesterday over health care, congressional earmarks, charter schools, and free speech, repeatedly shouting over one another as they aired significant distinctions on policy."