compression

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The act or process of compressing.
2. n. The state of being compressed.
3. n. The process by which the working substance in a heat engine, such as the vapor mixture in the cylinder of an internal-combustion engine, is compressed.
4. n. The engine cycle during which this process occurs.
5. n. Computer Science The process by which data is compressed into a form that minimizes the space required to store or transmit it.

Century Dictionary and Cyclopedia

1. n. The act of compressing, or the state of being compressed; a condition of being pressed into increased density or closeness: used in both literal and figurative senses.

Wiktionary

1. n. to increase in density; the act of compressing, or the state of being compressed; compaction
2. n. the cycle of an internal combustion engine during which the fuel and air mixture is compressed
3. n. the process by which data is compressed
4. n. the electronic process by which any sound's gain is automatically controlled

GNU Webster's 1913

1. n. The act of compressing, or state of being compressed.
2. n. reduction of the space required for storage (of binary data) by an algorithm which converts the data to a smaller number of bits while preserving the information content. The act of compressing {3}.

WordNet 3.0

1. n. encoding information while reducing the bandwidth or bits required
2. n. the process or result of becoming smaller or pressed together
3. n. applying pressure
4. n. an increase in the density of something