The Collaborative International Dictionary of English v.0.48:

Woof \Woof\ (w[=oo]f), n. [OE. oof, AS. [=o]wef, [=o]web,
   [=a]web; on, an, on + wef, web, fr. wefan to weave. The
   initial w is due to the influence of E. weave. See On,
   Weave, and cf. Abb.]
   [1913 Webster]
   1. The threads that cross the warp in a woven fabric; the
      weft; the filling; the thread usually carried by the
      shuttle in weaving.
      [1913 Webster]

   2. Texture; cloth; as, a pall of softest woof. --Pope.
      [1913 Webster]

WordNet (r) 3.0 (2006):

woof
    n 1: the yarn woven across the warp yarn in weaving [syn:
         woof, weft, filling, pick]