βασανιστής, -οῦ, ὁ (< βασανίζω), prop., a torturer; used of a gaoler, Mat.18:34.† (AS)
Thayer:
1) one who elicits the truth by the use of the rack 1a) an inquisitor, torturer also used of a jailer doubtless because the business of torturing was also assigned to him
βασανιστής
basanistēs
bas-an-is-tace'
From G928; a torturer