soaked or drenched; thoroughly wet.
雨で服がびしょびしょになった。
My clothes got soaking wet in the rain.
彼の靴は水たまりですっかりびしょびしょだ。
His shoes are completely soaked from the puddle.
魚を洗った後で台所がびしょびしょになった。
After washing the fish, the kitchen was sopping wet.
raining continuously or drizzling (used as an adverb describing rain).
夕方から小雨がびしょびしょ降り続いている。
A light rain has been drizzling on and off since evening.
傘を持っていなかったので、びしょびしょと濡れてしまった。
I didn't have an umbrella, so I got soaked in the persistent rain.