Stepped die

A stepped die is one that that can step up or down from its current value in the dice chain. The dice chain is typically the default D&D set of polyhedrals (1d4, 1d6, 1d8, 1d10, 1d12, 1d20) but sometimes other polyhederals like d30s are included or there are steps of +1 before the die size increases.

Stepping up or down simply means that the die size increases or decreases one step in the chain.

Stepped die are used in 24xx and Black Hack amongst other games.