WordNet (r) 3.0 (2006):

dot matrix printer
    n 1: a printer that represents each character as a pattern of
         dots from a dot matrix [syn: dot matrix printer, matrix
         printer, dot printer]

The Free On-line Dictionary of Computing (30 December 2018):

dot matrix printer

    A kind of printer with a vertical column
   of up to 48 small closely packed needles or "pins" each of
   which can be individually forced forward to press an ink
   ribbon against the paper.  The print head is repeatedly
   scanned across the page and different combinations of needles
   activated at each point.

   Dot matrix printers are noisy compared to non-impact
   printers.

   [Other pin arrangements?]

   (1995-03-14)