From Longman Dictionary of Contemporary Englishrainstormrain‧storm /ˈreɪnstɔːm $ -ɔːrm/ noun [countable] DNa sudden heavy fall of rain SYN downpour
Examples from the Corpus
rainstorm• Although they may get flattened by a rainstorm, they quickly recover once the sun comes out.• In minutes the sky had darkened and a heavy rainstorm was lacing the fields before me.• Everything from erosion to leaching to iron rainstorms is possible, perhaps much more.• It was the shortest rainstorm he'd ever seen.• Sadly, these dedicated servants end up standing in the blazing sun, a routine broken only by the occasional soaking rainstorm.• The day came, and with it a forty days, forty nights style rainstorm.• Rilla Challiss recalled, and there was no twilight, for a violent rainstorm began as night fell.• You can look at a whole rainstorm on a weather map. 