M
MAAC Mid-Atlantic Area Council (NERC Region, USA)
MAC Manual Alarm Call
MACHC MESO American & Caribbean Sea Hydrographic Committee  www.webpage
MACRS Modified Accelerated Cost-Recovery System  
MADL  Maximum Annual Daily Load 
MAHB Major Accident Hazards Bureau (European Commission)
MAIN Mid-America Interconnected Network (NERC Region, USA)
MAOP Maximum Allowed Operating Pressure
MAPP Mid-Continent Area Power Pool (NERC Region, USA)
Marad Maritime Administration 
MARPOL International Convention for the Prevention of Pollution by Ships www.website
MARS Major Accident Reporting System (Europe-MAHB)
Multiple Application Reinjection System (subsea well interface developped by DES)
MAST Marine Science and Technology program www.website
MAWP Maximum Allowed Working Pressure
MBES  Multi Beam Echo Sounder
MBbl thousand barrels 
Mboe  Thousand Barrels Oil Equivalent.
MBR  Minimum Bending Radius
MBSHC Mediterranean and Black Seas Hydrographic Commission (IHO) www.webpage 
MC Mechanical Completion
MCA  Maritime and Coastguard Agency (UK)
MCB  Miniature Circuit Breaker
MCC  Motor Control Center
MCCB Moult Cased Circuit Breaker
Mcf Thousand Cubic Feet (of natural gas)
MCFC Molten Carbonate Fuel Cell
MCM  Manifold Control Module
MCPC  Multiple Channels Per Carrier
MCR  Main Control Room
  Maximum Continuously Rated (output)
  Motion Comfort  Ratio (predicting the speed of the upward and downward motion of the boat as it encounters waves and swells
MCS  Multiple Service Contract
MCT Multi Cable Transit
MCV  Manifold Circulation Valve
MDE Marginal Detectable Error
MDF  Main Distribution Frame
MDI  Multiple Document Interface
MDL Methane Drainage Licence 
MDMC  Marine Division Management Committee (IMCA) 
MDP Maximum Design Pressure
MDPC  Marine Disaster Prevention Centre (Japan) www.website 
MDR Master Document Register
MDS  Material Data Sheet
MDT Modular formation Dynamics Tester 
MED Marine Environment Division (IMO website)
MEDEVAC Medical Evacuation 
MEDS Marine Environmental Data Service (Canada) www.website
MEPC IMO Marine Environment Protection Committee  
MEG  Maintenance Engineering Group
  Mean Effective Gain
  Mono Ethylene Glycol
  Motionless Electromagnetic Generator  
  Message Entry Generator  
MEK  Methyl Ethyl Ketone
MEL Main Equipment List
  Maximum Exposure Level 
MEMAC  Marine Emergencies Mutual Aid Centre (The Gulf) 
MEPC Marine Environment Protection Committee (IMO website)
MF  Medium Frequency 
MFI Melt Flow Index
MFR Mass Flow Rate
MGB  Mainr rotor Gear Box (helicopter)
MGI  Miscible Gas Injection 
MGL  Main Gas Line 
MHHW  Mean Higher High Water
MH Manhole
MHI  Material Handling Institute (USA) www.website 
  Material Handling Industry www.website 
MHWS  Mean High Water Spring 
MI Malleable Cast Iron
MIB Management Information Base
MIC  Maintenance Inhibit Console 
  Micro-biological Influenced Corrosion
MICC Mineral Insulated Cooper Cable 
MINCONMAR Ministerial Conference of West and Central African States on Maritime Transport
MIME  Managing Impacts in the marine environment 
MIST  Minimum Industry Safety Training (UK) 
MIV Methanol Injection Valve 
MLI Magnetic Level Indicator 
MLP Maximum Lawful Price
MLS Microwave Landing System
MLLW  Mean Lower Low Water
MLWS  Mean Low Water Springs
MM  Manifold Module
MMBbl Million Barrels
MMBoe   Million Barrels Oil Equivalent 
MMCB Mould Miniature Circuit Breaker
MMcf Millions cubic feet
MMcfd Millions of cubic feet per day (of gas). 
MMscfd Millions of Standard Cubic Feet per Day (of gas).  
MMscmd  Millions of Standard Cubic Metres per Day (of gas) 
MMMF  Man Made Mineral Fibre
MMI  Man Machine Interface
MMO  Mixed Metal Oxide 
MMS Minerals Management Service
MMSA  Materials & Methods Standards Association 
MMSCMD Million Standard Cubic Meter per Day
MMU  Measurement Management Unit 
  Motor Management Unit 
MOB Man Over Board 
MODU  Mobile Offshore Drilling Units 
MoHWG IHO Manual on Hydrography Working Group www.webpage
MOIG  Mediterranean Oil Industry Group www.website
MOL  Main Oil Line 
MOP Maximum Operating pressure 
MOPO Manual (Matrix) of Permitted Operations
MOPU Mobile Offshore Production Unit 
MOSFET  Metal Oxyde Semiconductor Field Effect Transistor
MOST Mechanical Outside Single Trip    
MOU  Memorandum of Understanding
MOV  Motor Operating Valve  
MP Medium Pressure 
MPA Marine Preservation Association (USA) MSRC website
  Marine and Port Authority  
MPB  Multi Purpose Basket 
MPC  Modular Platform Component 
MPCU Marine Pollution Control Unit (UK): term no longer in use after April 1999, now incorporated into MCA 
MPD Managed Pressure Drilling
MPE Magnetic Particle Examination 
MPI  Magnetic Particle Inspection 
MPMS Manual of Petroleum Measurements Standards 
MPP MultiPhase Pump
MPS Manufacturing Procedure Specifications
MPV  Multi Purpose Vessel
MQC  Mechanical Quick Connect 
MQP Manufactory Quality Plant 
MQR  Material Quality Report 
MRC  Marine Response Center
  Maximum Reservoir Contact 
MRCC  Maritime Rescue Co-ordination Centre
MRL Minimal Risk Level
MRU Motion Reference Unit 
MS Medium Strength 
  Marine Surveyor
MSA Manual/Stop/Auto 
MSC  IMO Maritime Safety Committee 
MSCHOA Maritime Security Center Horn Of Africa 
MSCL  Multi Sensor Core Logging 
MSDS Material Safety Data Sheet 
MSE  Mean-Squared Error
MSL Mean Sea Level 
mSOT minimum Service Operating Temperature
MSP Maximum Service Pressure 
MSPP Maritime Safety and Pollution Prevention (Directorate of the UK Coast Guard Agency - MCA)
MSRC  Marine Spill Response Corporation (USA) www.website
MSS  Manufacturers Standardization Society of the Valve and Fittings Industry. www.website
MST  Maximum Service Temperature 
mST  minimum Service Temperature 
MSV  Multi Support Vessel
Mt  Million tonnes 
MT Metric Tonne 
MTC  Medical Treatment Case 
MTBF  Mean Time Between Failure

MTEM 

Multi-Transient ElectroMagnetics (company)
MTHRT Mechanical Tubing Hanger Running Tool 
MTI Metal Treating Institute, Inc. (USA) www.website 
MTO  Material Take Off
MTOW  Maximum Take Off Weight
MTP  Maximum Test Pressure 
MTR  Main Telecom Room 
MTTR  Mean Time To Rescue/Repair 
MTU  Mobile Test Unit
MUMM Management Unit of the Mathematical Model of the North Sea  www.website
MV  Medium Voltage (= frencg BTB for Basse Tension B) i.e. 500<U<=1000 AC or 750<U<=1500 DC 
MVAR  Mega Volt Ampere Reactive  
MVR  Melt Volume flow Rate 
MW Molar mass (Weight) of a gas / Molecular Weight
  MegaWatt / Million of Watts
MWD Measurement While Drilling 
MWP Maximum Working Pressure 
  Multi Well Platform 
MWS  Marine Warranty Surveyor
MWT Maximum Working Temperature 
mWT minimum Working Temperature