| Strictly speaking, that of or pertaining to Asia. In ethnic terms it might be expected that it is a collective term for all peoples from the largest continent, but due to the vagaries of the English language and political correctness things aren't quite so clear-cut.
In the USA, Canada and Australia the term Asian is usually applied to those who are from the southeast asian region: China, Vietnam, Malaysia, Japan and nearby countries.
In Britain the term is applied mainly to those from the Indian subcontinent: people from India, Pakistan, Bangladesh and Sri Lanka.
Southeast Asian peoples are more commonly referred to as Oriental in Britain, however in the United States this is a pejorative term. Whereas in the US many people from the Indian subcontinent are labelled Hindus or Indians, again a term that would cause serious offence if used in the UK, especially if it was directed at a (Muslim) resident of Pakistan.
None of the above takes any account of other ethnic groupings from Asia, such as the Mongols of the Central Asian steppes, the Siberian people or those from the Persian (Iraq) area and many of the former Soviet Republics.
I suppose such are the complications of attempting to apply geographic terms to races of people, for human beings have the annoying habit of moving from place to place and refusing to be bound by artificial geographic boundaries. | 
