oakum

/ˈoʊkəm/
noun
  1. Loose fibers obtained by untwisting old ropes, used for caulking the seams of wooden ships or pipes.
    • The shipwright packed oakum into the gaps between the planks to make the hull watertight.
    • Sailors would spend hours picking apart tarred rope to make oakum for repairs.
    • Before modern sealants, plumbers used oakum to seal joints in cast iron pipes.
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