The Collaborative International Dictionary of English v.0.48:

Bunch \Bunch\, v. i. [imp. & p. p. Bunched; p. pr. & vb. n.
   Bunching.]
   To swell out into a bunch or protuberance; to be protuberant
   or round.
   [1913 Webster]

         Bunching out into a large round knob at one end.
                                                  --Woodward.
   [1913 Webster]