What does M stand for?

Mandatory

Compulsory, required or ordered by an official organisation or authority.

Maiden

Manchester

Mandibular

Manipulator

A remotely-operated work arm.

Manhattan

Manifold

A pipe or series of pipes connecting a series of ports to a common opening. A conductor with multiple connection ports, generally made from a solid block of metal with internally drilled passageways to minimize the amount of piping required.  A fabricated system of passages to which various components are attached to form a working assembly or subassembly. A term used mainly with reference to blow molding and sometimes with injection molding equipment.

Managua

Mandrel

A rod used to retain the cavity in hollow metal products during working. A metal bar around which other metal may be cast, bent, formed or shaped. A form, generally of elongated round section used for size and to support hose during fabrications and/or vulcanization. It may be rigid or flexible. A tapered expanding device, fixed in diameter which is pulled through a shank of a fitting thus expanding the diameter to exert force on the hose between the shank and ferrule.

Mantle

 Middle layer of the Earth; between the crust and the core. The mantle is the region inside the Earth that lies between the outer crust and the core. The layer below the crust; about 2,900 km thick; contains rocks rich in iron, magnesium, and silicon. The middle zone of the earth, between the core and the crust. The layer of the Earth immediately below the crust. Beneath the mantle is the core.