two-way mirror
From Longman Dictionary of Contemporary EnglishRelated topics: Daily lifetwo-way mirrorˌtwo-way ˈmirror noun [countable] Dglass that is a mirror from one side, but that you can see through from the otherExamples from the Corpustwo-way mirror• Lifeline 1990 consists of a two-way mirror, paint, light, timers and wood.• It had been a short honeymoon: one night in front of a two-way mirror.