The Jargon File (version 4.4.7, 29 Dec 2003):

bitblt
 /bit'blit/, n.

    [from BLT, q.v.:]

    1. [common] Any of a family of closely related algorithms for moving and
    copying rectangles of bits between main and display memory on a bit-mapped
    device, or between two areas of either main or display memory (the
    requirement to do the Right Thing in the case of overlapping source and
    destination rectangles is what makes BitBlt tricky).

    2. Synonym for blit or BLT. Both uses are borderline techspeak.


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

bitblt

   /bit'blit/ [BLT] 1. Any of a family of closely related
   algorithms for moving and copying rectangles of bits between
   main and display memory on a bit-mapped device, or between
   two areas of either main or display memory (the requirement to
   do the Right Thing in the case of overlapping source and
   destination rectangles is what makes BitBlt tricky).

   2. blit, BLT.

   [Jargon File]