Definition of METATARSAL. : of, relating to, or being the part of the human foot or of the hind foot in quadrupeds between the tarsus and the phalanges that in humans comprises five elongated bones which form the front of the instep and ball of the foot. See metatarsal defined for kids.ADVERTISEMENT. of, relating to, or being the part of the human foot or of the hind foot in quadrupeds between the tarsus and the phalanges that in humans comprises five elongated bones which form the front of the instep and ball of the foot. See metatarsal defined for kids. ADVERTISEMENT.