This word is often used - for many law and politics students in the context of "Parliamentary Sovereignty".
One of the first writers to discuss the concept was Jean Bodin (1529/30 - 1596), who published in 1576 "Les Six Livres de la Republique". Cambridge University Press have taken some of the chapters and published them as "On Sovereignty" which was edited by Julian Franklin
The context was that the idea of being "English" or "French" was changing from the feudal idea of being the subject of a particular king (as in "I am English because I owe my allegiance to the King of England") to being from a particular geographic area (the modern idea of "I am English because I was born/live permanently in England). Ideas of states based on geography, and have a single source of constitutional power began to develop.
Parliamentary Sovereignty is a concept based on that idea of there being a single source of power. Once the King was sovereign (this is not a pun!) - but after the English Civil War, and certainly after the "Glorious Revolution" in which Parliament 'chased James II out of town' and chose William and Mary to be the new Monarchs - it was recognised that power derives from Parliament. It can make or dissolve any institution (it can create, and subsequently abolish a Scottish Parliament; institutions of local government; Courts...); and define who can become King (Act of Settlement 1701).
Dicey is the most well known academic who sought to describe and define the principle. To slightly paraphrase him - it means
1 Parliament can pass any law it wants (unlike the US Congress which can have its laws struck down by the Supreme Court if in conflict with the Constitution)
2 A Parliament is not bound by its predecessors (so there can be no entrenched legislation which forces a later Parliament to use special procedures to change specific laws - like a 2/3 majority, or a referendum)
3 What Parliament has done cannot be questioned in the Courts (another aspect of the first meaning)
But Parliamentary Sovereignty has been challenged. It sits uneasily with British membership of the European Union. By passing the European Communities Act 1972. Our membership involves agreeing to limit our legislative freedom - and to be subject to decisions of the Court of Justice of the European Union.In the Thoburn case it was recognised that the usual principle of "implied repeal" didn't apply to the European Communities Act. Of course the answer to a claim that Parliamentary Sovereignty is dead - is that Parliament retains the sovereign right to repeal the European Communities Act.
Dicey is not the only view of the doctrine. There is an excellent, thought provoking book by Jeffrey Goldsworthy
Most Constitutional Textbooks rehearse the various arguments. If you are a law student - be sure that you are able to define the doctrine and discuss the various arguments about its strength today. Don't forget the importance of critically evaluating the arguments put forward by the various commentators.