En banc

Definition of En banc

L. Fr. In the bench. Full bench. Refers to a session where the entire membership of the court will participate in the decision rather than the regular quorum. In other countries, it is common for a court to have more members than sire usually necessary to hear an appeal. In the United States, the Circuit Courts of Appeal usually sit in panels of judges but for important cases may expand the bench to a larger number, when they are said to be sitting en banc. See Fed.R.App.P. 35. An appellate court in which all the judges who are necessary for a quorum are sitting as contrasted with a session of such court presided over by a single justice or panel of justices.

That's the definition of En banc in Black's Law Dictionary 6th Edition. Courtesy of Cekhukum.com.