the light that indicates which way you are going to turn while driving....a lever to left of the steering wheel is raised or lowered to start the flashing of the light
Most drivers these days are not aware that their cars come equipped with turn signals, or they are just too "busy" to use them- they expect other drivers to be psychic and figure out what exactly they are doing- it is infuriating!!!!!
With reference to the first definition about the turn signal being on the left. Of course, in England and Australia for example, which have right hand drive, the signal lever is on the right. I know from having experience.