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.

&fist; 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.

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.