The system of Government that exists in Great Britain and which has been copied, to a greater or lesser extent, by many Commonwealth countries; so called because it is named after the precint Westminster where the House of Commons and the House of Lords meet.

a particular type of parliamentary system in which the head of state has considerable reserve powers which are in practice limited strongly by convention rather than explicit constitutional rule

Australia's system of parliamentary democracy, inherited from the United Kingdom. The Westminster system focuses on control of government created by majority control of the Lower House of the Parliament, with Ministers selected from Members of Parliament to take responsibility for the executive arm of government (bureaucratic government departments and agencies). Ministers collectively form the Cabinet, headed by the Prime Minister, Premier or Chief Minister (in the case of the States and Territories), and are responsible for their actions to the Parliament and serve with the Parliament's confidence. This system of government is sometimes referred to as "responsible government".

A system of parliamentary government found in the United Kingdom and in many former British colonies which in general has most of the following characteristics (although they have evolved in different ways in different places and may exist to varying degrees): responsible government; members of the government are required to be Members of Parliament; a Parliament that is legally entitled to amend or repeal any law passed by its predecessors; a constitution with important parts that are unwritten; a non-partisan public service; and an independent judiciary.

The system of bi-cameral parliamentary government developed in Britain.

The Westminster system is a democratic parliamentary system of government modeled after that of the United Kingdom system, as used in the Palace of Westminster, the location of the Parliament of the United Kingdom. The system is a series of procedures for operating a legislature. It is also used, or was once used, in most Commonwealth and ex-Commonwealth nations, beginning with the Canadian provinces in the mid-19th century.