SIR Full Form. Full Meaning of SIR Find long form and abbreviation, slang or definition of SIR. What does SIR mean? What does SIR stand for? We are providing world largest and most comprehensive acronyms, names, abbreviations database directory on the Internet. Our data base contains more than 8,00,000 terms abbreviations and acronyms. You can also search unique terms more than 4,00,000 general Comprehensive words.