A room or small establishment where tea and light refreshments are served. Common in hotels, department stores, and traditional settings.
ホテルのティールームでアフタヌーンティーを楽しんだ。
We enjoyed afternoon tea at the hotel's tearoom.
喫茶店 is a more general Japanese term for a coffee shop or café, while ティールーム specifically emphasizes tea service and often a more refined atmosphere.
Loanword from English 'tearoom'.