From Longman Business DictionaryGenerally Accepted Accounting PrinciplesˌGenerally Acˌcepted Acˈcounting ˌPrinciples abbreviation GAAP noun [plural]ACCOUNTING in the US, official rules about how things should be dealt with and shown in company accounts. In Britain, similar rules are set down in the FINANCIAL REPORTING STANDARDSNew York state now requires the city of New York to balance its budget on the basis of Generally Accepted Accounting Principles.