Boiling mad

IRATE

Think of a five-letter word for furious that starts with the same letter as "infuriated."

"Boiling mad" is a common phrase meaning extremely angry, and "irate" is a synonym that fits perfectly. The word "boiling" hints at intense heat, reinforcing the idea of strong emotion, while "mad" directly points to anger. Since crossword clues often rely on straightforward synonyms, "irate" is the natural answer here.