Source : Free On-Line Dictionary of Computing

full-custom
     
        Design of {integrated circuit}s at the transistor or polygon
        level.  This is in contrast to the use of libraries of
        components.  Full-custom design requires considerable skill
        and experience and is usually only feasible for simple
        circuits, especially ones with much repetition, such as memory
        device, where a small saving in the size and power consumption
        of a component will yield a large overall saving.
     
        (1994-12-01)