\Bur\, Burr \Burr\, n. [OE. burre burdock; cf. Dan. borre,
OSw. borra, burdock, thistle; perh. akin to E. bristle (burr-
for burz-), or perh. to F. bourre hair, wool, stuff; also,
according to Cotgrave, ``the downe, or hairie coat, wherewith
divers herbes, fruits, and flowers, are covered,'' fr. L.
burrae trifles, LL. reburrus rough.]
1. (Bot.) Any rough or prickly envelope of the seeds of
   plants, whether a pericarp, a persistent calyx, or an
   involucre, as of the chestnut and burdock. Also, any weed
   which bears burs.
         Amongst rude burs and thistles.       --Milton.
         Bur and brake and brier.              --Tennyson.
2. The thin ridge left by a tool in cutting or shaping metal.
   See {Burr}, n., 2.
3. A ring of iron on a lance or spear. See {Burr}, n., 4.
4. The lobe of the ear. See {Burr}, n., 5.
5. The sweetbread.
6. A clinker; a partially vitrified brick.
7. (Mech.)
   (a) A small circular saw.
   (b) A triangular chisel.
   (c) A drill with a serrated head larger than the shank; --
       used by dentists.
8. [Cf. Gael. borr, borra, a knob, bunch.] (Zo["o]l.) The
   round knob of an antler next to a deer's head. [Commonly
   written {burr}.]
{Bur oak} (Bot.), a useful and ornamental species of oak
   ({Quercus macrocarpa}) with ovoid acorns inclosed in deep
   cups imbricated with pointed scales. It grows in the
   Middle and Western United States, and its wood is tough,
   close-grained, and durable.
{Bur reed} (Bot.), a plant of the genus {Sparganium}, having
   long ribbonlike leaves.