The Supreme Court staked out a definition for "supervisor" in the context of Title VII. Vance v. Ball State Univ., No. 11-556 (June 24, 2013). Whether a person is a "supervisor" determines whether the employer can be held strictly liable for the person's harassing conduct (because "supervisor" status aided in the accomplishment of the harassment), or whether the employer can only be liable if it was negligent.
In defining "supervisor," the Court refused to follow cases under the National Labor Relations Act and rejected the EEOC's guidance on the subject of "supervisor" status. According to the Supreme Court, a person is your "supervisor" if that person has authority from the employer to take "tangible employment actions" against you. Unfortunately, "tangible employment action" itself can be hard to define and whether a person has authority from the employer might be open to argument. A "tangible employment action" is a "significant change in employment status, such as hiring, firing, failing to promote, reassignment with significantly different responsibilities. or a decision causing a significant change in benefits." (Emphasis added.) The Court also cautions that the mere fact that someone else higher in a hierarchy has to approve the decision does not mean that only the higher person is a supervisor. If an employer tries to concentrate authority to hire and fire a few people, the Court expects that group would rely on effective recommendations from others in the organization and the employer "may be held to have effectively delegated the power to take tangible employment actions" against the individuals making recommendations.