A technology that allows several parties to collaborate and compute a function, while keeping their respective inputs private.
In a business context, this has been a huge advance for businesses looking to collaborate on their data (e.g. to build new data products), without having to share raw datasets. Secure multi-party computation is also useful in cases where regulations or trust-levels don't allow parties to share data between parties - e.g. across country borders. Often uses methods from homomorphic encryption.