The Collaborative International Dictionary of English v.0.48:

Teasel \Tea"sel\, v. t. [imp. & p. p. Teaseledor Teaselled;
   p. pr. & vb. n. Teaseling or Teaselling.]
   To subject, as woolen cloth, to the action of teasels, or any
   substitute for them which has an effect to raise a nap.
   [1913 Webster]