Compressor

A compressor is:

1. A mechanical device that takes in a gas and increases its pressure by squeezing a volume of it into a smaller volume. Heat is generated in the gas due to the ineffeciancy of the compressor. Important kinds of compressors include: Reciprocating compressors, Centrifugal compressors, and Turbo-charger. Closely related to pumps.
2. A device or computer program that reduces the dynamic range of a signal. In audio production, a compressor is often applied to the final mix as part of the mastering process. See audio level compression.