Source : Webster's Revised Unabridged Dictionary (1913)

Caliphate \Cal"i*phate\, n. [Cf. F. califat.]
   The office, dignity, or government of a caliph or of the
   caliphs.

Source : WordNet®

Caliphate
     n 1: the era of Islam's ascendaancy from the death of Mohammed
          until the 13th century; some Moslems still maintain that
          the Moslem world must always have a calif as head of the
          community; "their goal was to reestablish the Caliphate"
     2: the territorial jurisdiction of a caliph
     3: the office of a caliph