The Collaborative International Dictionary of English v.0.48:

Primordial \Pri*mor"di*al\, n.
   A first principle or element.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Primordial \Pri*mor"di*al\, a. [L. primordialis, from primordium
   the first beginning; primus first + ordiri to begin a web, to
   begin: cf. F. primordial.]
   1. First in order; primary; original; of earliest origin; as,
      primordial condition. "The primordial facts of our
      intelligent nature." --Sir W. Hamilton.
      [1913 Webster]

   2. (Geol.) Of or pertaining to the lowest beds of the
      Silurian age, corresponding to the Acadian and Potsdam
      periods in American geology. It is called also Cambrian,
      and by many geologists is separated from the Silurian.
      [1913 Webster]

   3. (Biol.) Originally or earliest formed in the growth of an
      individual or organ; as, a primordial leaf; a primordial
      cell.
      [1913 Webster]

   Primordial utricle (Bot.), the interior lining of a young
      vegetable cell.
      [1913 Webster]

WordNet (r) 3.0 (2006):

primordial
    adj 1: having existed from the beginning; in an earliest or
           original stage or state; "aboriginal forests"; "primal
           eras before the appearance of life on earth"; "the forest
           primeval"; "primordial matter"; "primordial forms of
           life" [syn: aboriginal, primal, primeval,
           primaeval, primordial]

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "primordial":
   aboriginal, ancestral, antepatriarchal, atavistic, autochthonous,
   basal, basic, central, crucial, elemental, elementary, embryonic,
   fundamental, generative, genetic, germinal, humanoid, in embryo,
   in ovo, original, patriarchal, preadamite, preglacial, pregnant,
   prehistoric, prehuman, primal, primary, prime, primeval, primitive,
   primogenial, primoprimitive, pristine, protogenic, protohistoric,
   protohuman, radical, rudimentary, seminal