Burr

noun

1. A sharp, pointy object, such as a sliver or splinter.
2. A bur; a seed pod with sharp features that stick in fur or clothing.
3. A small piece of material left on an edge after a cutting operation.
4. A thin flat piece of metal, formed from a sheet by punching; a small washer put on the end of a rivet before it is swaged down.
5. A broad iron ring on a tilting lance just below the grip, to prevent the hand from slipping.