Definition of "Axis" :

noun: the center around which something rotates

noun: the 2nd cervical vertebra; serves as a pivot for turning the head

noun: a straight line through a body or figure that satisfies certain conditions

noun: a group of countries in special alliance

noun: in World War II the alliance of Germany and Italy in 1936 which later included Japan and other nations

"The Axis opposed the Allies in World War II."

noun: the main stem or central part about which plant organs or plant parts such as branches are arranged