turtleneck vs polo-neck

turtleneck and polo-neck both are nouns.

Word	Noun	Adjective	Verb	Adverb
turtleneck	Yes	No	No	No
polo-neck	Yes	No	No	No

As nouns, turtleneck and polo-neck are synonyms defined as:

turtleneck and polo-neck: a sweater or jersey with a high close-fitting collar

Other synonyms of turtleneck include turtle.

turtleneck (noun)	polo-neck (noun)
a sweater or jersey with a high close-fitting collar	a sweater or jersey with a high close-fitting collar