bur / bər/ (also burr) • n. 1. a prickly seed case or flowerhead that clings to animals and clothes. ∎  [usu. as adj.] a plant that produces burs, e.g., bur reed.2. [as adj.] denoting wood containing knots or other growths that show a pattern of dense swirls in the grain when sawn, used for veneers and other decorative woodwork: bur walnut.3. variant spelling of burr (senses 2, 3, and 5).

bur (ber) n.
1. a cutting instrument that fits in a dental handpiece (see drill). Burs are mainly used for cutting cavities in teeth, removing old restorations, and preparing teeth to receive crowns.

2. (burr) a surgical drill for cutting through bone. b. hole a circular hole drilled through the skull to release pressure inside the skull or to facilitate biopsies and other procedures.

bur, burr3 rough or prickly seed-vessel or flower-head XIV. perh. of Scand. orig.; cf. Da. burre bur, burdock, Sw. kardborre burdock, perh. rel. to BRISTLE.

burr1 rough edge on cut metal, etc. XVII. prob. same word as BUR.
Hence as vb. XIX.