ATO Full Form. Full Meaning of ATO Find long form and abbreviation, slang or definition of ATO. What does ATO mean? What does ATO 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.