To Dilute
To Water Down
transitive verb, ichidan verb
Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means dilute and the verb vocab version means to dilute or to water down.
The reading comes from 薄い, so if you know that you'll be able to read this too.
この味噌汁はしょっぱすぎるよ。もうちょっと薄めてもらってもいいかな？
This miso soup is too salty. Can you water down a little bit?