The letters "MM" can have multiple meanings depending on their context. Here are some possible interpretations:
1. Millimeters (abbreviation for millimetres), which is a unit of length equal to one-thousandth of a meter or about 0.039 inches.
2. Months, as in "MM" can refer to the number of months that have passed since a specific date.
3. MegaMek, an abbreviation for Mega Mechanics, which is a popular game mechanic used in various role-playing games such as BattleTech and MechWarrior.
4. "MM" can also be used to express agreement or approval, similar to the use of "OK."