A camera move. The camera rotates on its mount from side to side. Usage: "pan left," "pan right." Non-filmmakers often make the error of saying "pan up" or "pan down" — this is actually a Tilt.
Short for panorama.
In some contexts, this sort of movement is called "yaw".
In traditional animation, pan refers to sliding the artwork under the camera (which is suspended vertically and locked in place). In that context, "pan up" and "pan down" are acceptable. Panning each level at a different speed creates Motion Parallax to give an illusion of depth.