| Term | Definition |
| Maffers | Working boater's term for Marsworth on the GU and for the top Marsworth Locks (Maffers 7). |
| Marines, Horse | A term used in Yorkshire for the horse haulage contractors that towed the keels on the canals. |
| Mast (on a working narrowboat) |  | A hollow square extendable post towards the front of the boat's hold used for attaching a towrope. |
| Mast Beam | The cross beam just ahead of the mast into which the mast is fitted. |
| Middle Beam | The cross beam behind the mast, which is slotted to take a stand. |
| Mitre Post | Also called a Head or Breast Post. The vertical post farthest from the hanging point of a lock gate. |
| Monkey boat | Slang term for a typical narrowboat. |
| Moria Cut | The Ashby Canal. |
| Moshers Two | Daw End Locks, BCN. |
| Mud Box | Working boater's term for the water intake filter on the engine cooling system. |
| Mud Heelers | Boaters working on the north Oxford Canal. |
| Mudding | Dredging by hand. |
| Nags Head Three | A working boater's term for the Seabrook Locks, Nos. 34 - 36, on the GU main line. |
| Narrow Boat | A craft, traditionally measuring approximately 70 feet long by 7 feet beam, used throughout the Midland canal system. Sometimes also referred to as a monkey boat or long boat. |
| Narrow canals | Narrow-gauge canals with restrictions of navigation at stop-locks to boats of less than 70 feet by 7 feet. |
| Navigation lamp | Oil or electric lamp displayed on or near the cratch of a narrowboat. Used for night work or in tunnels. |
| Navigation Weir | A weir with a single gate to allow navigation. Boats either had to navigate with, or against, the rush of water or to wait for the whole of pounds on either side of the weir to become equal. Also called a Staunch or Flash Lock. |
| Neals | A working boater's term for Slapton Lock, Nos. 30, on the GU main line. |
| Nip | A term used on the River Trent for a narrow place. |
| Noble | Working boater's term for Newbold on the Oxford Canal. |
| Northwich | Commercial narrowboats built by Yarwoods Ltd. at Northwich, Cheshire. |
| Number one | An owner-boater, mainly on the narrow canals. |
| Oakum | Lengths of shredded rope used with pitch to seal apertures between planks and such like. |
| Oil Rod | The speed control on a Bolinder engine. |
| Old Thirteen | Farmers Bridge Locks, BCN. |
| Open boats | Boats with no cabins. Often these were used as day boats. |
| Outside and Outside Turn | Outside is the boaters term for the side of the canal away from the towpath thus an outside turn is one where the deep water is on the opposite side to the towpath. |
| Oxford River | Working canal boaters term for the Thames above Reading. |
| Packet boat | Boat used in regular service for passengers, their hand luggage and small parcels. |
| Paddle | A slat, or small door, used to control the flow of water through a lock or weir. |
| Paddle Bar | The rod or shaft linking a paddle to the operating mechanism. |
| Pen | A fenland term for a lock. |
| Peters Two | A working boater's term for the bottom two Marsworth Locks, Nos. 37 & 38, on the GU main line. |
| Pigeon box | Oblong or box-shaped ventilator above the engine-hole hatch of a motorboat. |
| Pill | A tidal creek with a soft mud bottom. From the welsh pwll (pool). |
| Plank Staunch | An East Anglian staunch simply constructed of planks laid one above the other. |
| Pointing Doors | A fenland term mitred lock gates. |
| Pool | North of England term for a canal pound. |
| Pools | A working boater's term for Horton Lock, No. 31, on the GU main line. |
| Port Claytons | Narrowboats belonging to Thomas Clayton which carried oil between Ellesmere Port and the Black Country. |
| Portage | To lift craft out of the water and carry them past an obstruction such as a lock, weir or rapids. |
| Pot | The socket at the bottom of a lock which takes the gudgeon or tan pin. |
| Pound | The length of canal between two locks. This can vary from a few feet, at Bratch Locks, to many miles. |
| Pound Lock | The normal type of lock found on inland waterways, having a lock chamber with gates at either end and paddles to control the water level. See also Flash Lock. |
| Pup | A 9hp Bolinder engine. |
| Quant | A Norfolk term for a boat pole or shaft. |
| Quarrage | The small changes in the tide at the uppermost limit of tidal influence on the River Severn, sometimes as high as Diglis weir, Worcester. |
| Quarter Bits | A pair of ropes on a fen lighter attached from the fore end of the jambing pole to each side (or quarter) of the lighter in front. |
| Queaches | Wet spots near a canal. From Queachy meaning boggy. |
| Railway Basins | Basins built to provide a direct interconnection for the transfer of goods between the railway and canal. |
| Railway Boats or Station Boats | Narrowboats operated by railway companies to take goods to and from Railway Basins. |
| Ram's Head |  | The wooden rudder post on a butty usually decorated with rope work and sometimes with a horse's tail. |
| Rampers | On wooden boats the spikes driven laterally between adjacent planks to hold them together. |
| Reach | On a non-tidal river the stretch of water between locks or on the tidal river between bends or landmarks. |
| Red Ticket | Issued to boats with urgent cargoes enabling them to pass through closed locks. |
| Reed Rond | A Norfolk reed bank. |
| Ribbon Plates | Plates with pierced edges, prized as decoration for the working boater's cabin and still popular today. |
| Ricky | (1) Rickmansworth on the GU (2) A boat built by Walker Brothers of Rickmansworth. |
| Rimers | The posts holding the removable paddles in Thames weirs. |
| Ring Hole Deep | A boat so fully laden that the rings on the gunwale are awash. |
| Risers | A series of locks having no intermediate pounds, so that the top gates of one forms the bottom gates of the next. Also called staircase locks. |
| River Class Boat | (1) Tanker narrowboats owned by Thomas Clayton of Oldbury named after rivers. (2) British Waterways Authority narrowboats dating from 1959 also known as blue tops. |
| Road | (1) The canal route e.g. The Bottom Road (2) The state of the locks ahead i.e. good - most locks in our favour - or bad. |
| Rocking | Working boater's term for a cutting. |
| Roding | A Fenland term for cutting rushes or reed in a river, or cotting if they are uprooted. |
| Rodney boat | A neglected family boat with scratched paint and dull brasses. A floating slum. |
| Rods | Working boater's term for engine controls of the type fitted to Bolinder engines. |
| Rond | A Norfolk river bank. |
| Roving Bridge or Turnover Bridge | A bridge carrying the towing path across another canal or branch at the junction. |
| Royalty Class Boats | Boats of the GUCC fleet of the 1930s, launched to coincide with a programme of widening, dredging and modernisation on the line of the canal, between London and Birmingham. They were named after kings and queens and only six were constructed. |
| Runcorn Boat | The type of narrowboat used on and around the Bridgewater Canal. |
| Running blocks | Wooden blocks used to guide a towing rope. |
