A means of measuring the amount of magic a character can use in various role-playing games. Different spells usually have different MP costs to reflect the amount of energy the caster must put into the spell. If the caster runs out of MP, he usually cannot cast any more spells.
Games (that I know of) that use this system include:
This term is actually a technical, uncreative, generic term for mana, which appears more often in instructions than in games.