- main transformer
- mainplane
- maintenance schedule
- Mach meter
- main deck
- main line
- main road
- maintenance measure
- maneuvering load
- manoeuvring load
- magnetic detector
- maiden flight
- mail train
- main generator
- main rib
- make fast
- make water
- mammoth tanker
- map table
- map datum
- marine architect
- marine engineer
- marine
- marine hovercraft
- marine insurance
- maritime communication
- maritime terminal
- marker
- marshaling area
- marshalling yard
- mast
- mast crane
- mast foot
- master change
- manifold pressure
- manoeuvre
- map scale
- mapped depth
- marine engineering
- marine loss
- marine radar
- maritime peril
- measured ton
- measured value
- marshaling track
- marshalling area
- mass airflow
- mast rake
- master program
- master programme
- masthead
- match wagon
- mercantile marine
- merchant haulage
- merchant marine
- mere breakers
- Merrcator chart
- mechanical brake
- merchant navy
- merging control
- metropolitan railway
- mileage
- metropolitan railroad
- metals
- middle ordinate
- midship beam
- mileage point
- mine railway
- mile marker
- milestone
- mixed train
- mixed levitation
- mixed transport
- methane carrier
- milepost
- mine locomotive
- minipusher tug
- mixer bellcrank
- mobile jack
- model test
- modular construction
- moisture content
- mole
- momentary capacity
- money order
- monobeam system
- monorail conveyor
- mother ship
- motor grader
- mountain railroad
- mud shop
- mooring bitts
- mooring cleat
- mooring harness
- mosaic
- motion detector
- motive force
- motor brake
- motor ferry
- motor truck