lode·star / ˈlōdˌstär/ • n. a star that is used to guide the course of a ship, esp. Polaris. ∎ fig. a person or thing that serves as a guide: she was his intellectual lodestar.

lodestar a star that is used to guide the course of a ship, especially the pole star. The word is recorded from Middle English, and the first element means ‘way, course’. The figurative use developed early and was popular up to the 17th century; it was then revived in the early 19th century.