Definition of marrows:
(n) :
(uncountable) The substance inside bones which produces blood cells.
(n) :
A kind of vegetable similar to a large courgette, zucchini or squash.
(n) :
(figurative) The essence; the best part.
(n) :
(figurative) The inner meaning or purpose.
(n) :
(countable, medicine, colloquial) Bone marrow biopsy.
(n) :
(Geordie, informal) A friend, pal, buddy, mate.