tetragrammaton

from WordNet (r) 3.0 (2006)

Tetragrammaton
    n 1: four Hebrew letters usually transliterated as YHWH (Yahweh)
         or JHVH (Jehovah) signifying the Hebrew name for God which
         the Jews regarded as too holy to pronounce

from The Collaborative International Dictionary of English v.0.48

Tetragrammaton \Tet`ra*gram"ma*ton\, n. [NL., fr. Gr. ?; te`tra-
   (see {Tetra-}) + ? a letter.]
   The mystic number four, which was often symbolized to
   represent the Deity, whose name was expressed by four letters
   among some ancient nations; as, the Hebrew JeHoVaH, Greek
   qeo`s, Latin deus, etc.
   [1913 Webster]