கெட்டுப்போkeṭṭuppō(keṭṭuppoo)(3b intr)become useless or damaged because of decay, humidity, etc.; disintegrate because of rot; be spoiled; become useless or ineffective; become corrupt
Usage:
புத்தகங்களெல்லாம் மழையில் நனைந்து கெட்டுப்போய்விட்டனputtakaṅkaḷellām maḻaiyil naṉaintu keṭṭuppōyviṭṭaṉa
pustaham ellaam maḻeyle nanenju keṭṭuppooccu
These books all got drenched in the rain and have started to rot.