It's Italian for counselor or advisor and is not used in Italy in the sense that was popularized by the movie, The Godfather. There is no legal usage of the term in English speaking countries, only in Italy. In English speaking places (mostly US), it is a reference to a role in a mafia (often an actual lawyer...who is the crime family's lawyer).
Sometimes a consigliere is an accountant and sometimes legitimate businesses that are run by Italian-American families use the word to mean "accountant who runs the business just as much as the CEO does." They are often the auditor of the business.
I can't find any citations that aren't behind paywalls, but you can maybe find "
A Delicate Relationship" at your local library's digital resources. It makes the point that unlike members of the "Executive Family" who runs the business (whether legal or illegal), the consigliere is not a family member, but a highly trained outsider who is trusted as if family.
I didn't see why it came up here, but that's what it means.