adverb, adverb taking the 'to' particle
noisily (of water gushing, splashing, spraying, etc.)
Mimetic word describing the sound or manner of water flowing forcefully, splashing, or being poured noisily. Often used with と.
蛇口から水がじゃあじゃあ出ている。
Water is gushing noisily from the faucet.
子どもがバケツの水をじゃあじゃあとまいた。
The child splashed water from the bucket noisily.