Source : Webster's Revised Unabridged Dictionary (1913)

Burr \Burr\, v. i. [imp. & p. p. {Burred}; p. pr. & vb. n.
   {Burring}.]
   To speak with burr; to make a hoarse or guttural murmur.
   --Mrs. Browning.

Source : WordNet®

bur
     n 1: seed vessel having hooks or prickles [syn: {burr}]
     2: small bit used in dentistry or surgery [syn: {burr}]
     [also: {burring}, {burred}]

bur
     v : remove the burrs from [syn: {burr}]
     [also: {burring}, {burred}]

burring
     See {bur}