Co-op means played by people working together rather than against. A co-op mode, play co-op, co-op campaign.
In games it is the opposite of competitive, and split-screen co-op has been replaced almost entirely by playing online. The same shortening also names a cooperative shop, which is a quite separate thing.
1adjectiveco-opPlayed by people working together rather than against.
“My brother and I prefer co-op games, where we team up against the computer.”
co-op is a quality.
A shortening of cooperative, from Latin cooperari, to work together, from com plus operari, to work.
From cooperative, by shortening.
Etymology from Wiktionary, CC BY-SA
Practised in Games & Toys