1A prescribed code or rubric, such as a spoken incantation or recipe for a potion, supposed to produce effects by or as if by magic.

2A word or phrase which has assumed great influence or significance, especially as the embodiment of a principle or doctrine; a watchword, a byword.

3A simply accomplished and highly effective means to a desired end, especially (frequently in negative constructions) an expedient solution to a problem; a panacea.