n. 1 the inner region of certain organs or tissues usu. when it is distinguishable from the outer region or cortex, as in hair or a kidney. 2 the myelin layer of certain nerve fibres. 3 the soft internal tissue of plants. medulla oblongata the continuation of the spinal cord within the skull, forming the lowest part of the brain stem. medullary adj.
[ L, = pith, marrow, prob. rel. to medius middle ]