Judas window
noun1
A window enabling a prison guard to see into a cell without being seen by the prisoner.
- A prisoner may be confined nude in a cell with a Judas window and intruded upon periodically while there.1989, James P. Sterba, Creighton Peden, Freedom, equality, and social change, page 314:
- Luckily an officer happened to look through the judas-window in the door and rushed in to save the witness2017, Theodore Dalrymple, The Knife Went In: