splenius

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Either of two muscles of the back of the neck, extending from the upper vertebrae to the base of the skull, that rotate and extend the head and neck.

Century Dictionary and Cyclopedia

1. n. A broad muscle, extending from the upper part of the thorax, on the back and side of the neck, beneath the trapezius. In man the splenius arises from the nuchal ligament and from the spinous processes of the seventh cervical and of the first six dorsal vertebræ. In ascending the neck, it is divided into two sections— the splenius capitis, inserted into the occipital bone beneath the superior curved line, and partly into the mastoid process, and

Wiktionary

1. n. anatomy A broad muscle running up the top part of the back of the neck.

GNU Webster's 1913

1. n. (Anat.) A flat muscle of the back of the neck.

WordNet 3.0

1. n. either of two flat muscles that extend from the upper vertebrae to the base of the skull and serve to rotate or flex or extend the head and neck