Fire-breathing is an adjective that often describes someone or something that is angry, aggressive, or intimidating. There are several synonyms that can be used to convey a similar meaning. For example, a "ferocious" person or animal can be described as fire-breathing. "Fierce" and "ruthless" are other words that are often used to describe the same type of individual. Another synonym for fire-breathing is "hotheaded," which suggests someone who is quick to anger and easily provoked. "Spitting fire" is also a common idiom that can be used to describe someone who is extremely angry or aggressive.