En banc is French for "on the bench." The term refers to a special procedure where all judges of a particular court hear a case. When the court believes that the matters are especially complex or important, the en banc procedure will be used. See e.g. Calderon v. Thompson, 524 US 965 (1998). The appellate court in the United States usually takes a panel to review a complex matter, and only rarely will the en banc procedure be applied.
[Last updated in October of 2022 by the Wex Definitions Team]