Webster's Revised Unabridged Dictionary · 1913

Oakum

Oakum (ōk"um) , noun

[Anglo-Saxon ācumba; pref. ā- (compare German er-, Gothic us-, orig. meaning, out) + cemban to comb, camb comb. See Comb.]

1.
The material obtained by untwisting and picking into loose fiber old hemp ropes; -- used for calking the seams of ships, stopping leaks, etc.
2.
The coarse portion separated from flax or hemp in nackling. — Knight
Collocations (1)
White oakum , that made from untarred rope.