The Collaborative International Dictionary
White oakum
Oakum \Oak"um\ ([=o]k"[u^]m), n. [AS. [=a]cumba; pref. [=a]- (cf. G. er-, Goth. us-, orig. meaning, out) + cemban to comb, camb comb. See Comb.]
The material obtained by untwisting and picking into loose fiber old hemp ropes; -- used for calking the seams of ships, stopping leaks, etc.
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The coarse portion separated from flax or hemp in nackling.
--Knight.White oakum, that made from untarred rope.
Wiktionary
white oakum
n. oakum made from untarred rope