CAROTID is a 7 letter word that starts with C.

1. \Ca*rot"id\, n. [Gr. ?, pl., from ? heavy sleep: cf. F.
   carotide. The early Greeks believed that these arteries in
   some way caused drowsiness.] (Anat.)
   One of the two main arteries of the neck, by which blood is
   conveyed from the aorta to the head.
   
   Note: [See Illust. of {Aorta}.]
   
   

2. \Ca*rot"id\, Carotidal \Ca*rot"id*al\, a. (Anat.)
   Pertaining to, or near, the carotids or one of them; as, the
   carotid gland.