BLT

BLT /B-L-T/, /bl*t/ or (rarely) /belt/ n.,vt.  Synonym
   for {blit}.  This is the original form of {blit} and the
   ancestor of {bitblt}.  It referred to any large bit-field copy
   or move operation (one resource-intensive memory-shuffling
   operation done on pre-paged versions of ITS, WAITS, and TOPS-10 was
   sardonically referred to as `The Big BLT').  The jargon usage has
   outlasted the {PDP-10} BLock Transfer instruction from which
   {BLT} derives; nowadays, the assembler mnemonic {BLT} almost
   always means `Branch if Less Than zero'.