Disruption is the term used to refer to cards which in some way disrupt the opposing player's game plan.
Disruption usually happens in the form of hand and deck manipulation, particularly removing cards from the opposing player's hand or deck. Disruption may also be in the form of tech cards that affect the way a player can play their cards, such as Loatheb. Although unlike tech cards, cards with disruption effects are usually not aimed at a specific deck or deck archetype, and can instead be used against many different decks.
Disruption is mostly aimed at the hand and deck, as they are things which the other player usually cannot interact with. In a way, both the hand and deck can be seen as "safe zones" from your opponent, unlike the battlefield, and disruption tools aim to interact with these safe zones.
Cards with disruptive effects may be added to prevent uninteractive combo decks from being too strong.