n 1  :  one of the arterial branches in vertebrate embryos that exist in a series of pairs with one on each side of the embryo, that connect the ventral arterial system lying anterior to the heart to the dorsal arterial system above the alimentary tract, and that persist in adult fishes but are reduced or much modified in the adult of higher forms  2  :  ARCH OF THE AORTA .
 
 
 
Published under license with Merriam-Webster, Incorporated.  © 1997-2024.