Christendom

n. Christian world

Christendom, or Christenhood, in the widest sense, refers to Christianity as a territorial phenomenon: those countries where most people are Christians are part of Christendom. In the West the word Christendom sometimes refers to Roman Catholic nations that include the "Social Reign of Christ the King," the concept that a nation is subject to the authority of the Church.
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Noun
1. the collective body of Christians throughout the world and history (found predominantly in Europe and the Americas and Australia); "for a thousand years the Roman Catholic Church was the principal church of Christendom"
(synonym) Christianity
(hypernym) body
(part-meronym) church, Christian church

n. Christianity, religion which is based upon the teachings of Jesus Christ and his apostles

(n.)
The whole body of Christians.
  

(n.)
The profession of faith in Christ by baptism; hence, the Christian religion, or the adoption of it.
  

(n.)
The name received at baptism; or, more generally, any name or appelation.
  

(n.)
That portion of the world in which Christianity prevails, or which is governed under Christian institutions, in distinction from heathen or Mohammedan lands.