Magnetic declinationAngular distance between the geographic North and the magnetic one
magnetic deviationDifference between magnetic North and compass inclination; variation due to external elements, such as metal items near the compass; see also compass compensation
Magnetic needleOne of the two steel rhomboidal magnetic elements of a magnetic compass .
Main mast casePoint of the hull where the main mast terminal lays
Main royal sailYard and relative trapezoidal sail, located at the top of the mainmast, above the topgallant sail.
MainmastMain mast in multi-mast vessels. Main sail
MainsailSail inserted on the mast or the boom, generally triangle-shaped.
Mainsail furlerDrum fixed to the mast which allows to roll, partially or totally, the mainsail
Mainsail travellerHorizontal rail when the mainsail sheet carriage runs
MainstayA wooden or iron beam which supports a deck
ManholeOpening in a bulkhead or in the deck wide enough to let a person pass through
ManropeWooden or metal handrail, generally mounted on the deck house
Marine signalsLighhouses, lights, buoys which makes navigation safer
Maritime signalingCombined cardinal-lateral system
MarlineThin cable used for hand stitchings.
MarocchinoCable which joins two mast heads
MastTo fix a mast on its step
Mast footTerminal part at the base of the mast, usually on the relative mast-step
Mast head truckClosure at the mast top
Mast partnerHole in the deck where the mast passes through
MastingL' Set of masts and stays of a boat
Match raceRegatta between two identical boats
Maximum loadingThe highest wind intensity the sheets of a hoisted sail can bear
MaydayEmergency signal indicating an extreme danger
Meltemi. Etesian windSummer northern widn which blows in the Aegean Sea.
Mercator projectionType of projection of Earth's surface on maps
Mercatore.Belgian geographer who invented the homonymous projection
MeridiansA great circle of the Earth passing through the poles and perpendicular to parallelsThe Greenwich meridian also serves as the basis for the world standard time zone system. (UMT)
Metacentric heightDistance between metacenter and barycenter. It indicates the boat's stability
Mike.Term which represents ‚M‚ in the international phonetic alphabet..
Millibar.Unit of measuremnt of the atmosperic pressure, equal to 1000 dynes per square centimeter.
MistralWind which blows from North-West
Mistral.One-design sailing board designed by E. Prade; Olympic class since 1996. it measures 3,.80x0.68 m; with a 6-square-meter-sail area
MizzenThe smallest aftermost mast on a sailing vessel having more than one mast
Mizzen sailMainsail hoisted on the mizzen mast
Mizzen staysailSail above kitchen stack
Mizzen topgallant sailSquaresail hoisted on the mizzen mast
Moderate windLonger and choppier waves.Degree 4 in Beaufort Scale
Moonraker, moonsailA light squaresail set above a skysail
Moor - verb -To come alongside a quay
Moor - verb -, mooringTo stop the boat by fixing it to a pier or a quay through some ropes or an anchor.
Moor tightly head and stern - verb -To moor fore and aft, both to a pier and through anchors
Moore with two anchors aheadMooring which uses two anchors placed on the bottom laterally to the boat. The two anchoring lines are divided and they both leave from the bow fitting. Useful when weather is bad.
Mooring postHeavy structure, generally made of cement, on the sea bottom provided with a ring to which a mooring chain is fixed
Mooring-postReference point located on the coast
Morse.Telegraphic alphabet invented by Samuel Morse: it consists of a group of lines and points which represent all letters.
MotorsailerA boat which includes the features of both sailing and motor boats
Move onTo move a boat at a sufficient speed to manoeuvre
MPSAcronym of Multi Purpose Sail, an asymmetric sail similar to gennaker, used in cruises
MustafàAuxiliary rudder system. A mechanical instrument used on sailing boats to maintain a stable course in relation to wind.It is an authomatic pilot which doesn't use energy, which is important in long navigations.