All G&A a/c A/D a/r A/S a/s/l C/A See all meanings Idioms and phrases on a collision system idiom[ C/U ]   music   plural A’s or As in Western music, the sixth Be aware in the scale (= series of notes) that commences on the note C, or a list of notes according to this noteWhen the ancient Greeks adopted the alphabet, that they had no use for yo