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 ]   audio   plural A’s or As in Western new music, the sixth Observe in the scale (= number of notes) that starts on the Observe C, or possibly a list of notes according to this note[4] The Roman variety ?a? is located in most printed substanc