The Collaborative International Dictionary of English v.0.48:

IHVH \IHVH\ [Written also JHVH, YHVH.]
   A transliteration of the four constants forming the Hebrew
   tetragrammaton or "incommunicable name" of the Supreme Being,
   which in latter Jewish tradition is not pronounced save with
   the vowels of adonai or elohim, so that the true
   pronunciation is lost.

   Note: Numerous attempts have been made to represent the
         supposed original form of the word, as Jahaveh, Jahvaj,
         Jahve, Jahveh, Yahve, Yahveh, Yahwe, Yahweh, etc.
         [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

JHVH
    n 1: a name for the God of the Old Testament as transliterated
         from the Hebrew consonants YHVH [syn: Yahweh, YHWH,
         Yahwe, Yahveh, YHVH, Yahve, Wahvey, Jahvey,
         Jahweh, Jehovah, JHVH]