Burring

from The Collaborative International Dictionary of English v.0.48

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.
   [1913 Webster]