Kentucky Windage is the practice of applying a horizontal adjustment of the point of aim for wind (windage) without the use of any physical or mechanical adjustments on the weapon.

Literally everyone, ever. Including the writer of this definition.

When shooting a rifle, the adjusted point of aim when compensating for wind.

A guess or SWAG at a subject. A fudge factor.

From the term for roughly aiming a rifle while allowing for any crosswind.