Definition of “rain” - Learner’s Dictionary

rain

noun uk us /reɪn/

A1 [ U ] water that falls from the sky in small drops:

heavy rain
It looks like rain (= as if it will rain).
the rains

[ plural ] in tropical countries, the time of year when there is a lot of rain:

They were waiting for the rains to come.
→ See also acid rain

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