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'.