A
member of the
Privy Council.
Originally the monarch's qurom for discussing how the country should be run, Privy Counsellors were the other great and good of the land (usually powerful
Barons,
Lords, and
Knights) offering advice to the monarch, in effect a pre-parliamentary
Cabinet.
In Britain as the Privy Council actually emerged into a parliamentary Cabinet, the fact remained that all members of the Cabinet had to be made Privy Counsellors, in order to access important information on "Privy Council" terms and to ensure loyalty to the monarch - and so it remains today. In order to become a Privy Counsellor you have to take the secret Privy Counsellor Oath.
Other people usually made into Privy Counsellors are the Archbishops of York and Canterbury, the leader of Her Majesty's loyal opposition, and Prime Ministers of former British colonies (Canada, Australia, Fiji, etc). Nowadays the practical benefits of being a Privy Counsellor are not the same as 13th century feudal England, however you do get to put the prefix Rt. Hon. in front of your name forever which means your postman will always know you used to be a important Government person and will always get the best tables at expensive restaurants.