A burr

[bur] /bɜr/
noun
aaron, 1756–1836, vice president of the u.s. 1801–05.
burr1
/bɜː/
noun
a small power-driven hand-operated rotary file, esp for removing burrs or for machining recesses
a rough edge left on a workpiece after cutting, drilling, etc
a rough or irregular protuberance, such as a burl on a tree
(brit) a burl on the trunk or root of a tree, sliced across for use as decorative veneer
noun, verb
a variant spelling of bur
verb (transitive)
to form a rough edge on (a workpiece)
to remove burrs from (a workpiece) by grinding, filing, etc; deburr
word origin
c14: variant of bur
burr2
/bɜː/
noun
(phonetics) an articulation of (r) characteristic of certain english dialects, esp the uvular fricative trill of northumberland or the retroflex r of the west of england
a whirring sound
verb
to pr-nounce (words) with a burr
to make a whirring sound
word origin
c18: either special use of bur (in the sense: rough sound) or of imitative origin
burr3
/bɜː/
noun
a washer fitting around the end of a rivet
a blank punched out of sheet metal
word origin
c16 (in the sense: broad ring on a spear): variant of burrow (in obsolete sense: borough)
burr4
/bɜː/
noun
short for buhrstone
a m-ss of hard siliceous rock surrounded by softer rock
word origin
c18: probably from bur, from its qualities of roughness
burr
/bɜː/
noun
aaron. 1756–1836, us vice-president (1800–04), who fled after killing a political rival in a duel and plotted to create an independent empire in the western us; acquitted (1807) of treason
burr
n.

“rough sound of the letter -r-” (especially that common in northumberland), 1760, later extended to “northern accented speech” in general. possibly the sound of the word is imitative of the speech peculiarity itself, or it was adapted from one of the senses of bur (q.v.), perhaps from the phrase to have a bur in (one’s) throat (late 14c.), which was a figure of speech for “feel a choking sensation, huskiness.” oed says the scottish -r- is a lingual trill, not a true burr.

burr (bûr)
n.
variant of bur.