the total amount of rain that falls in a particular area in a particular amount of time; an occasion when rain falls There has been below average rainfall this month. an average annual rainfall of 10 cm Wordfinderarid, climate, continental climate, equatorial, frigid, harsh, humidity, rainfall, tropical, zone See related entries: RainExtra examples The area has a high annual rainfall. There have been heavy rainfalls this month. We need a good rainfall to save the crops. We have an average annual rainfall of around 750 mm.