Each subsequent attack or every nth attack is more powerful than the last. Usually going in chains of 3 to 5 attacks that reset at the end, and sometimes resetting when swapping targets or pausing for too long between attacks.
Alternate name: Attack progression
The first video game about Progressive attacks was released in 1995.
An example of multi-button progressive attack instead of combo would be. If you have 2 attacks and they have 3 states each that progress linearly. Allowing player to swap between attacks but not canceling the progression state would in effect be still progressive attack without an actual combo. For example, kick 1, kick 2, kick 3 would be normal progression, but then you could to punch 1, punch 2, kick 3, or kick 1, punch 2, kick 3, and so forth. The attacks would be identical to their progression state no matter what you had for the other progression states, so no actual combo moves are performed.