1.of no importance or relevance especially to a law case;
an objection that is immaterial after the fact
2.without material form or substance;
an incorporeal spirit
3.not consisting of matter;
immaterial apparitions
4.not pertinent to the matter under consideration;
an issue extraneous to the debate
5.(often followed by `to') lacking importance; not mattering one way or the other;
whether you choose to do it or not is a matter that is quite immaterial (or indifferent)