Spiral is a method that allows opener to further describe opener’s single raise of responder’s suit. Here is a sample auction:
East’s two notrump is Spiral: artificial, asking for artificial rebids by opener: three clubs promises three spades and a minimum, three diamonds promises three spades and a maximum, three hearts promises four spades and a minimum, and three spades promises four spades and a maximum. We recommend Spiral for partnerships that allow opener to raise with three-card support.
The usual version of Spiral is that responder bids two notrump to start Spiral, whether responder’s suit is spades or hearts.