Source : Webster's Revised Unabridged Dictionary (1913)

Slubbing \Slub"bing\,
   a. & n. from {Slub}.

   {Slubbing billy}, or {Slubbing machine}, the machine by which
      slubs are formed.

Slub \Slub\, v. t. [imp. & p. p. {Slubbed}; p. pr. & vb. n.
   {Slubbing}.]
   To draw out and twist slightly; -- said of slivers of wool.