Minute of Angle
Also: MOA
An angular unit equal to 1/60th of a degree, roughly 1.047 inches at 100 yards. Most American precision optics dial in 1/4 or 1/8 MOA clicks.
MOA is one of two standard angular units used on precision optics. Because it’s based on degrees, the math is intuitive for an American audience: an MOA covers a hair over an inch at 100 yards, two inches at 200, ten inches at 1,000.
A scope with 1/4-MOA clicks adjusts the reticle 1/4 inch per click at 100 yards, half an inch at 200, and so on. Useful precision for inside 800 yards. For ELR work, mil is increasingly the standard.