Multi-signature address

Definition
A multi-signature address

"needs two (or more) different keys on different machines for the transaction to work, and therefore means no one person can authorise the transfer of funds, making it more difficult for someone to steal units of digital currency from that address. It may also be useful for organisations or groups that would like a majority vote to confirm the transaction, meaning all shareholders can have a key and the funds are only used when there is an agreed majority."