vt. 1. To copy a large array of bits from one part of a computer's memory to another part, particularly when the memory is being used to determine what is shown on a display screen. "The storage allocator picks through the table and copies the good parts up into high memory, and then blits it all back down again."
More generally, to perform some operation (such as toggling) on a large array of bits while moving them.
2. All-capitalized as 'BLIT': an early experimental bit-mapped terminal designed by Rob Pike at Bell Labs, later commercialized as the AT&T 5620. (The folk etymology from 'Bell Labs Intelligent Terminal' is incorrect.)