Webster's Revised Unabridged Dictionary · 1913

Prop

Prop , noun

A shell, used as a die. See Props.

Prop , transitive verb

[Akin to LG. & Dutch proppen to cram, stuff, thrust into, stop, German pfropfen, Danish proppe, Swedish proppa; of uncertain origin, compare German pfropfen to graft, from Latin propago set, layer of a plant, slip, shoot. Compare 3d. Prop, Propagate.]

To support, or prevent from falling, by placing something under or against; as, to prop up a fence or an old building; (Figuratively) to sustain; to maintain; as, to prop a declining state. — Shakespeare
Till the bright mountains prop the incumbent sky. — Pope
For being not propp'd by ancestry. — Shakespeare
I prop myself upon those few supports that are left me. — Pope

Prop , noun

[Akin to LG., Dutch, & Danish prop stopple, stopper, cork, Swedish propp, German pfropf. See Prop, v.]

That which sustains an incumbent weight; that on which anything rests or leans for support; a support; a stay; as, a prop for a building.
Two props of virtue. — Shakespeare