A small restaurant where you go mainly to drink tea and eat something light with it — cake, scones, sandwiches. It is a British word, and it carries a whole picture with it: quiet, small, a bit old-fashioned, often with flowered cups and tablecloths, the kind of place you might find in a country village, a museum, or an old department store. Older customers, no loud music, no one rushing you out.

That picture is why the word feels the way it does. A modern shop selling bubble tea or takeaway coffee would not be called a tearoom, even though it sells tea — the word promises somewhere you sit down and slow down. English people sometimes use it warmly and sometimes with a smile, to say a place feels gentle and behind the times.

Written as one word tearoom, or as tea room or tea-room; all are normal. Note also that in older American slang tearoom meant a public toilet where men met other men — this is a completely separate, dated, and rather hidden use, and you will almost never meet it, but it is why the word can raise an eyebrow in the US.