/ ˈmærəʊ; NAmE -roʊ/ noun
1.
[ U ] = bone marrow
2.
( BrE ) [ U , C ] a large vegetable that grows on the ground. Marrows are long and thick with dark green skin and white flesh.
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WORD ORIGIN
Old English mearg , mærg (in sense 1), of Germanic origin; related to Dutch merg and German Mark . Sense 2 dates from the early 19th cent.