a Lacanian term (following the linguistics of Saussure); really just another signifier (i.e., something that organises discursive structures) but one which stops the slippage of the signified under the signifier and fixes meaning, thereby forming a stable symbolic order. i don't really know tbh. a platonic ideal of a concept like "freedom" or "health"?
A basic feature of our postmodern world is that it tries to dispense with this agency of the ordering Master- Signifier: the complexity of the world needs to be as serted unconditionally. Every Master-Signifier meant to impose some order on it must be deconstructed, dis persed