Multisignature (multisig) refers to requiring more than one key to authorize a transaction. It is generally used to divide up responsibility for possession of a cryptocurrency.
For example, standard transactions on the Bitcoin network could be called “single signature transactions” because transfers require only one signature….from the owner of the private key associated with the Bitcoin address.
However, the Bitcoin network supports much more complicated transactions that require the signatures of multiple people before the funds can be transferred.