- main beam
- main loudness
- major chord
- major seventh
- majorana force
- maneuver
- manoeuvrability
- magnetic film
- magnetic flux
- magnetic shield
- magnetometry
- major second
- major third
- maneuverability
- Marx generator
- mask microphone
- masking effect
- masking index
- mass assignment
- mass density
- mass distribution
- mass matrix
- master control
- manoeuvre
- manual handling
- manual shutdown
- manual transmission
- many-electron
- materials handling
- mathematical particle
- matrass
- matt collar
- matt paper
- matte box
- maximize
- Maxwell distribution
- measurement reactor
- maser
- masking frame
- mass
- mass balance
- mass defect
- mass fraction
- mass spectrometry
- mechanical composting
- mechanical hazard
- mechanical motion
- mechanical oscillation
- mechanical properties
- mechanical reactance
- mechanical recording
- mechanical resistance
- mechanical splice
- mechanical stage
- mechanical susceptance
- mechanical vibration
- mechanism
- mechatrnics
- mediant
- megascope
- megavolt
- Meissner effect
- melt down
- meltable
- melting bath
- melting time
- meniscus
- meat machine
- mechanical admittance
- mechanical bond
- mechanical chopper
- mechanical classifier
- mechanical compliance
- mechanical editing
- mechanical force
- mechanical shock
- mechanical system
- media
- megadoc
- megawatt
- megohm
- melting period
- melting range
- melting test
- melting-point
- membrane loudspeaker
- mercury intensification
- metastable atom
- microelectromechical system
- micromillimeter
- microscope condenser
- microsope
- meson
- metastable
- meteorological optics
- Michelso interferometer
- micropit
- microscopic state
- microwave optics
- mesotron