Praetorium

The Greek word (praitorion) thus rendered in (Mark 15:16) is rendered "common hall" [(Matt 27:27), marg., "governor's house"], "judgment hall," (John 18:28; 18:33), marg., "Pilate's house", (John 19:9; Acts 23:35), "palace" (Phil 1:13). This is properly a military word. It denotes

(1) the general's tent or headquarters;

(2) the governor's residence, as in (Acts 23:35) (R.V., "palace"); and

(3) the praetorian guard (See PALACE), or the camp or quarters of the praetorian cohorts (Acts 28:16), the imperial guards in immediate attendance on the emperor, who was "praetor" or commander-in-chief.

EBD - Easton's Bible Dictionary