1. of or pertaining or relating to the planet pluto; of or pertaining to or resembling pluto the god of wealth and god of the underworld; of or pertaining to the underworld. plutonianplu*toni*an , a. [l. plutonius, gr. : cf. f. plutonien.] plutonic.plutonian plu*toni*an , n. (geol.) a plutonist.plutonian of or relating to or characteristic of hades or tartarus [syn: hadean, plutonian, tartarean]