This word used by someone to confirm the act
said by another person must be done, similar to "Tell her". If
said sentence is banked and then not completed then the speaker is a twat and everyone ignores them until
said sentence occurs.
Banks can be revoked, but only by the person whom placed the bank upon the speaker.
It derives from the popular game show "The Weakest
Link", in which the word 'Bank' is spoken by a member of the team whom wishes to bank money already gained.
Henry: Would you moonie that
car over there?
George: Yeah of course.
Henry: Bank.
George: *Moonies the
car*
George: I may as well just get my dick out now.
Fred: Bank.
George: *Gets his dick out*
John: Look, there's that guy who never did his 'Bank', let's ignore him forever.