[1] : The Collaborative International Dictionary of English v.0.48

chthonic \chthon"ic\, a. gr. ?, ?, the earth.
   pertaining to the earth; earthy; as, chthonic religions.
   1913 webster

         the chthonic character of the wife of zeus. --max
                                                  m"uller.
   1913 webster chthonophagia

[2] : WordNet (r) 2.0

chthonic
     adj : of the underworld; "nether regions" syn: chthonian, lower,
            nether
see also:
chthonian lower nether 

Chthonic >> C Words
Chthonic, definition of term: Chthonic
chthonic_pag1.html