M
- Maximummer
- A problem in which black must make the geometrically longest moves available to him, as measured from square-centre to square-centre. If two or more longest moves of equal length are available, black may choose between them. This stipulation is most often attached to selfmates.
- Meredith
- A problem with no less than eight and no more than twelve pieces on the board in the starting position. A problem with less than eight pieces is a miniature.
- Miniature
- A problem with no more than seven pieces on the board in the initial position.
- Model mate
- A pure mate in which all white units, with the possible exception of king and pawns, are involved in the mate. A particular feature of problems by members of the Bohemian School.
- More-mover
- A directmate with the stipulation "White to move and checkmate Back in no more than n moves against any defence" where n is greater than 3. In composition tourneys, there are often separate classes for more-movers, two-movers and three-movers (as well as classes for helpmates, selfmates and others).
- Motif
- An element of a move in the consideration why the piece moves and how it supports the fulfillment of the problem stipulation.
- Mutate
- A type of block problem in which at least one mate in the set play is changed following the key.
Read more about this topic: Glossary Of Chess Problems