I couldn't miss the chance to practice my drawing!
Multi-targeting is a support ability in the Final Fantasy. Usually spells which have this attribute can have their multi-casting effect toggled, while other spells may forcibly effect an entire party.
Most spells can be multi-targeted by having the Materia attached to an All Materia. Mega All makes nearly all spells and attacks multi-target. The multi-targeting attribute can be assigned to command abilities.