The Collaborative International Dictionary of English v.0.48:

Ido \I"do\ ([=e]"d[=o]), n.
   An artificial international language, selected by the
   "Delegation for the Adoption of an Auxillary International
   Language" (founded at Paris in 1901), made public in 1907,
   and subsequently greatly revised and extended by a permanent
   committee or "Academy." It is a revised and simplified form
   of Esperanto. It combines systematically the advantages of
   previous schemes with a thoroughly logical word formation,
   and has neither accented constants nor arbitrarily coined
   pronominal words. For each idea that root is selected which
   is already most international, on the principle of the
   "greatest facility for the greatest number of people." The
   word "Ido" means in the language itself "offspring." The
   official name is: "Linguo Internaciona di la Delegitaro
   (Sistema Ido)." -- I"dism, n. -- I"dist, n.
   [Webster 1913 Suppl. +PJC]

WordNet (r) 3.0 (2006):

Ido
    n 1: an artificial language that is a revision and
         simplification of Esperanto