Source : Webster's Revised Unabridged Dictionary (1913)

Prop \Prop\, v. t. [imp. & p. p. {Propped}; p. pr. & vb. n.
   {Propping}.] [Akin to LG. & D. proppen to cram, stuff, thrust
   into, stop, G. pfropfen, Dan. proppe, Sw. proppa; of
   uncertain origin, cf. G. pfropfen to graft, fr. L. propago
   set, layer of a plant, slip, shoot. Cf. 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;
   (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.

Source : WordNet®

prop
     n 1: a support placed beneath or against something to keep it
          from shaking or falling
     2: any movable articles or objects used on the set of a play or
        movie; "before every scene he ran down his checklist of
        props" [syn: {property}]
     3: a propeller that rotates to push against air [syn: {airplane
        propeller}, {airscrew}]
     [also: {propping}, {propped}]

prop
     v : support by placing against something solid or rigid; "shore
         and buttress an old building" [syn: {prop up}, {shore up},
          {shore}]
     [also: {propping}, {propped}]

propping
     See {prop}