Counter

Counter is the action of invalidating your opponent's spell or ability.

Details
It is taken from Magic: The Gathering terminology.

The ability is exclusive to Supernova Mercury Gigablizzard, and only against the effect of spells.

The similiar ability of "Do Not Trigger" is also seen on Wald Brachio, Absolute World King and Keshikasu, Vanish King.

A deck with a many cards of this ability is known as "permission" as it causes your opponent "to ask permission" whether they can resolve their cards into play. However, this deck type is limited in Duel Masters due to being exclusive to Gigablizzard.