turn signal vs visual signal

turn signal and visual signal both are nouns.

Word	Noun	Adjective	Verb	Adverb
turn signal	Yes	No	No	No
visual signal	Yes	No	No	No

As nouns, visual signal is a hypernym of turn signal; that is, visual signal is a word with a broader meaning than turn signal:

turn signal: a blinking light on a motor vehicle that indicates the direction in which the vehicle is about to turn
visual signal: a signal that involves visual communication

turn signal (noun)	visual signal (noun)
a blinking light on a motor vehicle that indicates the direction in which the vehicle is about to turn	a signal that involves visual communication