crew neck

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A round close-fitting neckline.
2. n. A garment, especially a sweater, with such a neckline.

Wiktionary

1. adj. Referring to the collar of pullover garments, where the collar circles the neck, usually of sweaters and T-shirts. Often crew necked.
2. adj. 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.
3. n. Any garment with a crew neck.

WordNet 3.0

1. n. a plain straight neckline opening from shoulder to shoulder of sweaters