What is the meaning of Prone?

Lying face-down.

Of the hand, forearm or foot: turned facing away from the body; with the thumb inward or big toe downward.

Having a downward inclination or slope.

Shooting from a position while lying down.

Predisposed, liable, inclined.

To place in a prone position, to place face down.

feminine plural of prono

vocative masculine singular of prōnus

leaning downwards, pronely

slanting, leaning

readily, willingly

Source: wiktionary.org