medulla (Noun) — A white fatty substance that forms a medullary sheath around the axis cylinder of some nerve fibers.
medulla (Noun) — Lower or hindmost part of the brain; continuous with spinal cord. ex. "the medulla oblongata is the most vital part of the brain because it contains centres controlling breathing and heart functioning"
medulla (Noun) — The inner part of an organ or structure in plant or animal.