Rain or other precipitation with a high concentration of acids produced by sulfur dioxide, nitrogen dioxide, and other such gases that result from the combustion of fossil fuels: it has a destructive effect on plant and aquatic life, buildings, etc.
Webster's New World
Direct contact - Can kill plant life depending on the plant’s sensitivity to acid.
On Organisms - Acid rain in the water can also wipe out entire species of organisms. Fish and other life forms in the water are extremely susceptible to acid rain.
An example of acid rain is rain near a coal factory that kills the plants around it.