The word "IRS" is an acronym that stands for Internal Revenue Service, which is the tax collection agency of the United States. Synonyms for this term can vary depending on the context. For instance, in casual conversations, people may use phrases like "tax man" or "tax collector" as synonyms for IRS. In formal contexts like legal documents or business contracts, other synonyms like "taxing authority" or "taxation department" might be used. Additionally, some people may use euphemistic phrases like "revenue agency" or "taxation bureau" to refer to the IRS. Regardless of the synonym used, it is important to know that the IRS is responsible for collecting taxes and enforcing tax laws in the U.S.