metanephros
noun
meta·neph·ros ˌme-tə-ˈne-frəs 
-ˌfräs
plural metanephroi ˌme-tə-ˈne-ˌfrȯi
: either member of the final and most caudal pair of the three successive pairs of vertebrate renal organs that functions as a permanent adult kidney in reptiles, birds, and mammals but is not present at all in lower forms compare mesonephros, pronephros
metanephric
ˌme-tə-ˈne-frik
adjective 
Word History
Etymology
New Latin, from meta- + Greek nephros kidney — more at nephritis
First Known Use
1877, in the meaning defined above
Medical Definition
metanephros
noun
meta·neph·ros -ˈnef-rəs, -ˌräs
plural metanephroi -ˌrȯi
: either member of the final and most caudal pair of the three successive pairs of vertebrate renal organs that functions as a permanent adult kidney in reptiles, birds, and mammals but is not present at all in lower forms compare mesonephros, pronephros