The Collaborative International Dictionary of English v.0.48:

Pur \Pur\, v. i. [imp. & p. p. Purred; p. pr. & vb. n.
   Purring.] [Of imitative origin; cf. Prov. G. purren.]
   To utter a low, murmuring, continued sound, as a cat does
   when pleased. [Written also purr.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pur \Pur\, v. t.
   To signify or express by purring. --Gray.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pur \Pur\, n.
   The low, murmuring sound made by a cat to express contentment
   or pleasure. [Written also purr.]
   [1913 Webster]