O.M.A stands for "Oh, my Athiest!" Like 'OMG' but for an Athiest to say.
Say "Oh, my Athiest" when someone says something rediculous, or crazy
-Person 1 - "O.M.A, I just got a dub sack from this stranger I met behind that building outside of Chicago next to my grandmas house.
-Person 2 - "Right on bro!"