also: ざーざーぶり · ざあざあぶり
noun
downpour; drenching rain
Describes heavy, continuous rain with a strong onomatopoeic feel. Often used in weather reports or casual conversation.
外はザーザー降りだから、傘を持って行ったほうがいいよ。
It's pouring outside, so you'd better take an umbrella.
ザーザー降りの雨の中を歩いて、びしょ濡れになった。
I walked in the downpour and got soaked.
Compound of the onomatopoeia ザーザー (sound of heavy rain) and 降り (rainfall).