Turtleneck (noun)

1. A high, close-fitting collar that folds over and covers the neck.
2. A sweater or shirt with a turtleneck collar.

Origin:

From the resemblance of the collar to the neck of a turtle.

Examples:

1. She wore a black turtleneck sweater to the party.
2. The turtleneck is a classic fashion statement.
3. I find turtlenecks to be quite comfortable and warm.
4. Turtleneck are often used as a layering piece in colder weather.
5. The turtleneck can be worn casually or dressed up for a more formal look.