SUBSONIC Meaning of SUBSONIC in English sub ‧ son ‧ ic /ˌsʌbˈsɒnɪk◂ $ -ˈsɑː-/ BrE AmE adjective slower than the speed of sound ⇨ supersonic Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012