intransitive verb, ichidan verb
Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means ripen so the verb vocab version is to ripen.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you: If something starts to ripen too much, it gets all gross, and you're all like, "ew (う), that's gross."
It’s about the time of year for peaches to ripen.