Definition:
Refers to the pH of the soil. A pH of 7 is neutral. Anything less than 7 is considered acidic. Acidic soils are sometimes referred to as "sour"
There are plants that prefer acidic soil, such as azaleas, rhododendrons and blueberries. If what you want to plant does not prefer an acid soil, you can raise the pH with amendments such as lime.
Examples:
The soil in my lawn tested at a 5.2 pH. That is much too acidic for growing grass, which prefers a pH in a 6.2 - 6.8 range.
