1) Muscle in the human neck 
• (a.) Of or pertaining to the sternum and the mastoid process.
(stur″no-mas´toid) pertaining to the sternum and the mastoid process.
Ster`no·mas'toid adjective (Anat.) Of or pertaining to the sternum and the mastoid process. 
Type: Term Pronunciation: ster′nō-mas′toyd Definitions: 1. Relating to the sternum and the mastoid process of the temporal bone; applied to the sternocleidomastoid muscle.
The sternomastoid is a muscle in the human neck.