drush sql-sync @live @dev

Array
(
    [default] => Array
        (
            [default] => Array
                (
                    [driver] => mysql
                    [username] => www-data
                    [host] => localhost
                    [database] => drupaldb
                )
            [mirror] => Array
                (
                    [driver] => mysql
                    [username] => www-data
                    [host] => localhost
                    [database] => mirrordrupaldb
                )

        )
    [other] => Array
        (
            [default] => Array
                (
                    [driver] => mysql
                    [username] => www-data
                    [host] => localhost
                    [database] => otherdb
                )

        )

)