1. adj. A term which means a spell can be "stacked" with another spell simultaneously. For example, Spirit Warding I and Spirit Warding II can both be in effect on a character at the same time, thus they are stackable. However, Kai's Song of Triumph and Eonak's Song of Glory cannot be in effect simultaneously, so those spellsongs are not stackable. Most spells in GemStone III are "stackable" with each other.

2. adj. The more common (yet incorrect) usage of the term "stackable," used to refer to spells with a cumulative duration. A spell with a cumulative duration can be cast more than once to extend the length of time the spell will last.