With all (or a majority or quorum) of the judges of a court present; before or by the full bench.
While in banc is preferred in some jurisdictions, en banc is now more usual; see B. A. Garner Garner's Dict. Legal Usage (2011) 315/2.
That is heard, conducted, or arrived at by or with all (or a majority or quorum) of the judges of a court present; (of a court) sitting in banc.
Early 19th century; earliest use found in Bell's Weekly Messenger. Apparently partly (i) an alteration of in bank or its model in banco.