noun

• (historical) A broad iron ring on a tilting lance just below the grip, to prevent the hand from slipping.
• (historical) A metal ring at the top of the hand-rest on a spear.
  "And there kyng Arthur smote syr mordred vnder the shelde wyth a foyne of his spere thorughoute the body more than a fadom / And whan syr Mordred felte that he had hys dethes wounde / He thryst hym self wyth the myght that he had vp to the bur of kynge Arthurs spere / And right so he smote his fader Arthur wyth his swerde holden in bothe his handes"
• (engineering) A revolving disk or cone with abrasive surfaces used to grind hard products in a grinder or mill.

verb

• (transitive, engineering) To grind using a burr (revolving disk or cone with abrasive surfaces).

verb

• (transitive) To pronounce with a uvular "r".
• (intransitive) To make a rough humming sound.
  "The first thing Lucy noticed as she went in was a burring sound, and the first thing she saw was a kind-looking old she-beaver sitting in the corner with a thread in her mouth working busily at her sewing machine, and it was from it that the sound came."

noun

• (British) Alternative spelling of burl.