With the possible exception of pdq, no one posting seems to have any idea of what the term Caucasian entails. It has been limited and expanded and twisted in many ways for political and cultural advantage, and no longer has meaning in common speech, although it remains a good overall term for talking about certain features, physical, linguistic and to some extent cultural, of a large group of people.

The term refers to the large group of peoples, more or less closely related, who extend from India and western Asia to Europe and North Africa. They share certain features, one being light to brown skin. Included are the people of the Caucasus, but they are a small part of the whole. The name was selected by anthropologists for the group because the Caucasus region is sort of geographically central to the widespread area occupied by the many peoples of the group.

Genome study is modifying patterns to some extent, but biologic and demographic factors are determinant. Genome study has determined a common origin or ancestry for humans, but human genetic variation is important to many studies including medicine.

A parallel term in language study is Indo-European, a group of languages which are spoken over much the same area.

One of the more peculiar decisions of the U. S. Supreme Court (1923) was with regard to an Asian Indian, Bhagat Singh, who the court said was Caucasian, but like other Asian Indians, was not 'white.'
Of course this had to do with naturalization, at the time limited to whites. This denied Singh's suit for citizenship. This ruling was changed in 1946.