Meaning of “flat” - Learner’s Dictionary

flat

noun [ C ] us uk /flæt/ UK mainly US apartment
Extra Examples
I live by myself in a small flat.He showed me round the flat.He lives in a block of flats.They live in a two-bedroom flat.I'll have the flat all to myself this weekend.

A1 a set of rooms to live in, with all the rooms on one level of a building:

a large block of flats

(Definition of “flat noun” from the Cambridge Learner’s Dictionary © Cambridge University Press)