Boyd’s Bible Dictionary:
The jurisdiction and charge of a bishop (Acts 1:20; 1 Tim. 3:1).
Concise Bible Dictionary:
ἐπισκοπή. The word is “office” in Psalm 109:8, which passage is quoted in the New Testament where the office, is “apostleship,” for which one was chosen to take the place of Judas Iscariot (Acts 1:20).