The Debris is an enemy in Final Fantasy XIII-2. Unlike most other creatures of the Bomb type, who bear a specific elemental weakness, Debris is not weak to any elements whatsoever.
Instead, using non-elemental magical attacks such as Ruin are necessary in order to stop them from growing and eventually self-destructing. Because of this, the player should use a paradigm with multiple Commandos, such as Cerberus (COM/COM/COM) or Aggression (COM/COM/RAV), in order to defeat them quickly and safely.
Debris is rubble, wreckage, ruins, litter and discarded garbage/refuse/trash, scattered remains of something destroyed, discarded, or as in geology, large rock fragments left by a melting glacier etc. Depending on context, debris can refer to a number of different things.