What is rampage ability in magic?

Answer 1

Rampage is a triggered ability on creatures and is written as Rampage followed by a number (E.g. Rampage 2).

When a creature with rampage is blocked it, gets +X/+X until the end of turn for each creature that blocked it beyond the first one, where X is the value written after rampage.

E.g. If a creature with Rampage 2 was blocked by a single creature, it would gain no bonus to its power and toughness; if it was blocked by two creatures it would get +2/+2 until end of turn; if it was blocked by three creatures it would get +4/+4 until end of turn, etc.

Answer 2

'Rampage X' - Whenever this creature becomes blocked, it gets +X/+X until end of turn for each creature blocking it beyond the first.

Basically it punishes your opponent for multiple blocking.