In the course of his normal work the seaman uses the word strain as meaning the pull or tension on a rope (e.g. 'take the strain' and 'a rope under strain'), which is the sense given in the dictionary.
Kwindlela eyiyo yomsebenzi indoda yaselwandle isebenzisa igama umsonto ukuchaza utsalo okanye ukutsaleka kwentambo (e.g. thatha umsonto kunye nentambo engaphantsi komsonto) isisivo esinikwe kwisichazi magama.