Source : Webster's Revised Unabridged Dictionary (1913)

Semiofficial \Sem`i*of*fi"cial\, a.
   Half official; having some official authority or importance;
   as, a semiofficial statement. -- {Sem`i*of*fi"cial*ly}, adv.

Source : WordNet®

semiofficial
     adj : having some official authority or sanction