Definition of labouring oar in English:
labouring oar
noun
(US laboring oar)
An oar that works or is worked, especially with difficulty or great effort; (hence figurative) the most difficult or demanding part of an enterprise (now chiefly US). Frequently in "to pull (also tug, ply) the labouring oar" (and variants).
Origin
Early 17th century; earliest use found in Michael Drayton (1536–1631), poet.
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