Source : Webster's Revised Unabridged Dictionary (1913)

Buttress \But"tress\, n. [OE. butrasse, boterace, fr. F. bouter
   to push; cf. OF. bouteret (nom. sing. and acc. pl. bouterez)
   buttress. See {Butt} an end, and cf. {Butteris}.]
   1. (Arch.) A projecting mass of masonry, used for resisting
      the thrust of an arch, or for ornament and symmetry.

   Note: When an external projection is used merely to stiffen a
         wall, it is a pier.

   2. Anything which supports or strengthens. ``The ground
      pillar and buttress of the good old cause of
      nonconformity.'' --South.

   {Flying buttress}. See {Flying buttress}.

Buttress \But"tress\, v. t. [imp. & p. p. {Buttressed} (?); p.
   pr. & vb. n. {Buttressing}.]
   To support with a buttress; to prop; to brace firmly.

         To set it upright again, and to prop and buttress it up
         for duration.                            --Burke.

Source : WordNet®

buttress
     n : a support usually of stone or brick; supports the wall of a
         building [syn: {buttressing}]
     v 1: reinforce with a buttress; "Buttress the church"
     2: make stronger or defensible; "buttress your thesis"