Arm ball - should be renamed away- (or in-) swinger.
This is what commentators say when the off-spin bolwer bowls a seam-up delivery with backspin that swings away from the right handed batter in the air and bounces further away after landing (or when a leg-spin bowler does the same delivery and the ball swings and seams into the right hander).
Arm ball - what's that supposed to mean?
Why is the delivery going 'with the arm'. The point about an effective 'arm ball' is that the arm movement is exactly the same as for the spun delivery - the difference is not in the arm but the hand/ fingers.
And surely the arm is not going in the same direction as the ball anyway, indeed how could it? since the ball curves and angles away - whereas the arm goes in a smooth circular trajectory.
Pooh! - 'arm ball' indeed. Why not call it what it is? - an away-swinger (for the off-spinner to the right handed batter) or an inswinger (for the left-arm orthodox finger spinner to the right handed batter.
After all the so-called arm ball is bowled pretty much the same way as the classical swung delivery fram a seam bowler - side-on action, seam angled towards the direction of intended swing, back-spin on the seam...
Swing it is.