crew neck

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A round close-fitting neckline.
• noun A garment, especially a sweater, with such a neckline.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective Referring to the collar of pullover garments, where the collar circles the neck, usually of sweaters and T-shirts. Often crew necked.
• adjective Occasionally, a collar whose front is meant to ride up onto the neck, sometimes to Adam's apple level, more often termed as high crew.
• noun Any garment with a crew neck.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a plain straight neckline opening from shoulder to shoulder of sweaters