Pronunciation: (kum-pres'ur),[key] —n. 1. a person or thing that compresses.
2. Anat.a muscle that compresses some part of the body.
3. Surg.an instrument for compressing a part of the body.
4. a pump or other machine for reducing volume and increasing pressure of gases in order to condense the gases, drive pneumatically powered machinery, etc.
5. Electronics.a transducer that produces an output with a range of voltages whose ratio is smaller than that of the range of the input signal. Cf. expander (def. 2).