—n. 1. a rough, prickly case around the seeds of certain plants, as the chestnut or burdock.
2. any bur-bearing plant.
3. something that adheres like a bur.
4. Mach.burr1 (defs. 1, 3).
5. Dentistry.a rotary cutting tool usually of steel or other hard metal shaped into a shank and a head, for removing carious material from teeth and preparing cavities for filling.
6. Surg.a cutting tool resembling that of a dentist, used for the excavation of bone.