SO-SO Meaning of SO-SO in English I. ˈsō-ˈsō adverbDate: circa 1530: moderately well : tolerably II. adjectiveDate: 1542: neither very good nor very bad : middling a so-so performance Merriam-Webster's Collegiate English vocabulary. Энциклопедический словарь английского языка Merriam Webster. 2003