- medianA central vein or nerve, especially the median vein or median nerve running through the forearm and arm.
- mezzanineAn intermediate floor or storey in between the main floors of a building; specifically, one that is directly above the ground floor which does not extend over the whole floorspace of the building, and so resembles a large balcony overlooking the ground floor; an entresol.
- mizzenMizzenmast.