"Collaborative transaction."

A CoinJoin is not necessarily a spend in the conventional sense. Some are, e.g. PayJoins.

I am strongly in favor of saying "collaborative transactions" as often as possible, because that's what they are.

It's also useful to point out that every transaction can be understood as a "smelting" process, i.e. all inputs are destroyed, and new outputs are created. Always. Many transactions have multiple inputs and outputs, e.g. batch transactions. Collaborative transactions are a feature of Bitcoin; some collaborative transactions improve your privacy.