1. the inner part of an organ or structure in plant or animal
2. lower or hindmost part of the brain
continuous with spinal cord
(`bulb' is an old term for medulla oblongata)
e.g. the medulla oblongata is the most vital part of the brain because it contains centers controlling breathing and heart functioning
Synonym: medulla oblongatabulb
3. a white fatty substance that forms a medullary sheath around the axis cylinder of some nerve fibers