Compressor \Com*press"or\, n. [L.]

Anything which serves to compress; as:
   (a) (Anat.) A muscle that compresses certain parts.
   (b) (Surg.) An instrument for compressing an artery (esp., the femoral artery) or other part.
   (c) An apparatus for confining or flattening between glass plates an object to be examined with the microscope; -- called also compressorium.
   (d) (Mach.) A machine for compressing gases; especially, an air compressor.

Source: Webster's Revised Unabridged Dictionary (1913)