one-way mirror
two-way mirror

At the bottom a one-way mirror gave him a view of the corridor outside.

The interviews took place in front of a one-way mirror, with students observing on the other side.

Matt spread his hands, and looked toward the one-way mirror.

In the privacy of our one-way mirror, I pointed at the screen.

Aaron led them to a locked door with a one-way mirror.

He looked back at the one-way mirror and stuck out his tongue.

Will hung up and stared across his office at the large one-way mirror.

We had kind of forgotten he was even there, behind his one-way mirror.

There was a one-way mirror so that officers could watch the interrogation from the next room.

People in mission control can see into the capsule through a one-way mirror.