Magic Jumars
Three pitch series off Alternative Universe (1997)
Man Friday
10m long continuation of Robinson Crusoe across FCII, containing unexplained footprint (1991)
The Mathematical Bridge
A rock arch in Flat Battery below Fifty Francis' Phreatic Freehang (1990)
Maud's Window
A hole in the Mathematical Bridge (1990)
Maze
Complex area to left of Vom pitch (1991)
The Meeting Room
Pitch beyond Fear-On traverse above Interview Blues (1996)
Mental Imbalance
Pitch below No Goer in Doubting Thomas (1995)
Mid Life Crisis
13m eighth pitch, beyond the Gravy Train in Interview Blues (1996)
Midnight in Moscow
55m pitch beyond Somebody Else's Problem in Siberia (1998)
Millennium Falcon
Squeezey bit in Bladerunner (1992)
Minoan Surprise
Short section left at Trifurcation containing 2 big shafts and expected to connect to Knossos (1995) [and proven correct (1996)]
Mississippi
Dried up river passage, right at T-junction reached by traversing big muddy shelf 15m down Sultans of Swing (1994) named for river of one of explorers' home town. Only traversed for a short way on main route, the rest is effectively a side passage leading to Black Suspender. The passage is also described coming from France.
Mississippi Mud Pie
Chocolate-mud filled passage, left at T-junction from 15m down Sultans of Swing (opposite direction from Mississippi) (1994)
Mohr in Hemd
Scrotty passage on right 15m from start of Mississippi (1994)
Moomintroll
Short passage reached by 3m climb down from Zebedee (1996)
Mosquito Coast
Awkward, tight, 8m third pitch in Bladerunner (1992)
Mostly Mud
Sordid keyhole passage beyond Silent Fellow (1992)
Moth Chamber
Hole in floor 60m beyond the Overflow in Triassic Park (1995) - the way in to Wheelchair Access (1996)
Mother of All Deviations
5m-off-the-rope deviation 44m down the first 80m pitch of Henri's Cat (1996)
Mothshag
Chamber near Scarface. Contained many shagging moths on discovery (1995)