acid precipitation

noun

1. meteorological precipitation that is relatively acidic.

1. Any form of precipitation, including rain, snow, hail, fog, or dew, that is high in acid pollutants, especially sulfuric and nitric acid. Acid precipitation has a pH of less than 5.6 (the normal acidity of unpolluted atmospheric water) and is often less than pH 5.0. Also called acid rain See Note at acid deposition.