Judicial supremacy is the view that the judiciary, and in particular the US Supreme Court, has special authority in constitutional interpretation that places the court superior to the other branches of government. Under judicial supremacy, the branches of government are not co-equal. Instead, under judicial supremacy, courts are above checks and balances by other branches of government.
Judicial supremacy was most clearly asserted by the Warren Court in Cooper v. Aaron (1958).
The better, and more traditional, view is that the US Constitution itself is the supreme law of the land, and that three branches of the federal government (Legislative, Executive, Judiciary) are equally responsible for upholding the Constitution and for applying checks and balances against usurpation in power by a rival branch.