instruction sets] 1. vi. To move oneself to the left (right). To move out of the way. 2. imper. "Get out of that (my) seat! You can shift to that empty one to the left (right)." Often used without the `logical', or as `left shift' instead of `shift left'. Sometimes heard as LSH /lish/, from the PDP-10 instruction set. See Programmer's Cheer.