pro·neph·ros \(ˈ)prō|nefrəs, -ˌfräs\noun alsopro·neph·ron\-_frən, -ˌfrän\ (pluralproneph·roi \-ˌfrȯi\ ; alsoproneph·ra \-_frə\) Etymology: New Latin, from pro- (I)+ Greek nephros kidney — more at nephritis : one of the anterior of the three pairs of embryonic renal organs of higher vertebrates