What does "prop" mean?

Additional senses

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