Boyd’s Bible Dictionary:
Pilate’s residence in Jerusalem
(John 18:28,33; 19:9). Praetorium or court (Acts 23:35).
Concise Bible Dictionary:
The word is πραιτώριον, prætorium, as it is translated in Mark 15:16. It was the official residence of Pilate the governor in Jerusalem (John 18:28, 33; John 19:9; Acts 23:35). It is translated “palace” (the barracks of the Praetorian body of soldiers, from whom Paul’s guards were selected) in Philippians 1:13; “common hall” in Matthew 27:27; and “hall of judgment” in John 18:28.