Source : Webster's Revised Unabridged Dictionary (1913)

Immaterial \Im`ma*te"ri*al\ ([i^]m`m[.a]*t[=e]"r[i^]*al), a.
   [Pref. im- not + material: cf. F. immat['e]riel.]
   1. Not consisting of matter; incorporeal; spiritual;
      disembodied.

            Angels are spirits immaterial and intellectual.
                                                  --Hooker.

   2. Of no substantial consequence; without weight or
      significance; unimportant; as, it is wholly immaterial
      whether he does so or not.

   Syn: Unimportant; inconsequential; insignificant;
        inconsiderable; trifling.

Source : WordNet®

immaterial
     adj 1: of no importance or relevance especially to a law case; "an
            objection that is immaterial after the fact" [ant: {material}]
     2: without material form or substance; "an incorporeal spirit"
        [syn: {incorporeal}] [ant: {corporeal}]
     3: not consisting of matter; "immaterial apparitions"; "ghosts
        and other immaterial entities" [syn: {nonmaterial}] [ant:
        {material}]
     4: not pertinent to the matter under consideration; "an issue
        extraneous to the debate"; "the price was immaterial";
        "mentioned several impertinent facts before finally coming
        to the point" [syn: {extraneous}, {impertinent}, {orthogonal}]
     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)";
        "what others think is altogether indifferent to him" [syn:
         {indifferent}]