godan ~る verb / intransitive verb:

• to become muddy; to become cloudy; to get impure (of a liquid, gas, etc.)
• to become dull (of a sound, color, etc.); to become hoarse
• to become impure (of a heart, society, etc.); to be corrupted; to be polluted
• to become voiced; to add voiced consonant marks ➜ 濁り【にごり】