semafor.

semaphore; railway signal (signaling device used in railways to convey information)

semaphore; business sign (two-sided advertising sign mounted on a building wall perpendicular to it, often with a business's logo, etc.)

semaphore (coastal device in the form of a mast with movable arms, showing ships the direction and strength of the wind)

semaphore (signaling system in shipping in which someone makes specific hand movements while holding special flags)

semaphore (bit, token, fragment of code, or some other mechanism which is used to restrict access to a shared function or device to a single process at a time, or to synchronize and coordinate events in different processes)