Administrative Interpretations of Judicial Decisions: Deference?

There is an interesting exchange of footnotes between the majority and dissenting opinions of the Supreme Court of the United States in Vance v. Ball State University (2013), 570 U.S. _____. At issue was the scope of Title VII of the Civil Rights Act. Previously, the Court had held that vicarious liability attaches to an employer for workplace harassment committed by a "supervisor". But what did "supervisor" mean?