The definition of a refugee comes from the 1951 Convention relating to the Status of Refugees and its 1967 Protocol (“Refugees Convention”).  This treaty forms part of international law.  It was drafted by country representatives at the United Nations and presented for ratification by countries in 1951.  Australia played a leading role in drafting the treaty and was one of the first ten countries to ratify it.  As a signatory to the Refugees Convention, Australia has voluntarily agreed to provide protection for refugees in its territory.  Refugees have certain rights under this treaty, the most important being protection from being sent back to their country of origin against their will.
 
The Refugees Convention defines a refugee as:

“Any person who owing to a well founded fear of being persecuted for reasons of race, religion, nationality, membership of a particular social group or political opinion, is outside the country of his/her nationality and is unable, or owing to such fear, is unwilling to avail himself/herself of the protection of that country.”

The important parts of this definition are:

• that the person has to be outside their country of origin;
• the reason for their flight has to be a fear of persecution;
• the persecution has to result from one or more of 5 grounds (race, religion, nationality, membership of a particular social group or political opinion);
• this fear of persecution has to be well founded; and
• the person is unwilling or unable to seek the protection of their country.

The term "refugee" is often used incorrectly, used to refer to people who have been displaced due to a natural disaster (eg an earthquake or volcanic eruption) or environmental change.  However, this usage is not strictly correct.

The UNHCR