burr

n. 1 a whirring sound. B rough sounding of the letter r. 2 (also bur) a rough edge on metal or paper. B surgeon's or dentist's small drill. 3 var. Of *bur 1, 2. v. Make a burr. [imitative]

n. 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.