Wiktionary
minute of angle
n. An angle, one sixtieth (1/60th) of a degree, used by gunners as a measurement of accuracy. One minute of angle is roughly equal to 1 inch at 100 yards distance.
Usage examples of "minute of angle".
With a suppressor attached, the thing was capable of minute of angle accuracy at six hundred meters.
In tests at the Aberdeen Proving Grounds it had recorded an incredible 1/2-minute of angle (MOA) at over 1000 yards.