SLUB
slub, knot, burl
(noun) soft lump or unevenness in a yarn; either an imperfection or created by design
Source: WordNet® 3.1
Noun
slub (plural slubs)
A small thickened portion or knot found on linen yarn, caused by defects.
Fabric fiber produced by slubbing.
Verb
slub (third-person singular simple present slubs, present participle slubbing, simple past and past participle slubbed)
To draw and twist fibers in order to prepare them for spinning.
Source: Wiktionary
Slub, n. Etym: [Etymol. uncertain.]
Definition: A roll of wool slightly twisted; a rove; -- called also
slubbing.
Slub, v. t. [imp. & p. p. Slubbed; p. pr. & vb. n. Slubbing.]
Definition: To draw out and twist slightly; -- said of slivers of wool.
Source: Webster’s Unabridged Dictionary 1913 Edition