This term is often used in reference to RPGs, where it is employed in the context of an ability. E.g. "Ability A has higher DPCT than ability B". What does this term mean / signify?
Damage per cast time
The term refers to the effective "dps contribution" that casting an ability does. The total damage an action contributed divided by the time it took.
The simplest examples are from turn-based RPGs, where actions frequently consume one 'unit slice' of time or one 'turn'. Note that some RPGs can have variable-length turns, where the length of the turn might depend on the character's stats and/or the selected move.
Let's consider an example for the simple case: Character C has 2 abilities, call them
- poison. Does 10 damage each turn for 3 turns, including the turn that you cast it.
- fireball. Fireball does 25 damage.
Let's say our hypothetical enemy has 110 health.
To kill the enemy in the optimal number of turns, our character should cast
Poison -> Poison -> Fireball -> Fireball, assuming the two instances of Poison count separately. The dpct then of the casts of Fireball are obvious, 25. Since the Damage/turn was 27.5, some simple math gets you the dpct of the poison casts: 30.
It's a useful measure to compare abilities for dealing damage when the plain damage numbers of the spell are complicated, to ask ourselves the question "Which ability should I cast now".