undertail adjective 2noun 2forms 1 adjective2 •Beneath a tail. •On the underside of the tail. noun2 •The ventral part of the tail of a bird. •The underside of a tail.The whiptail wallaby is a slender, long-tailed, long-limbed macropod. […] its belly and the base of its undertail are white; the rest of its tail, feet and paws are dark. — 2005 formsundertails
