Sentence:  Let us return to the laboratory, where Bob is about to lift the tarp off of the transparent box containing <WSD>Schrödinger's cat</WSD>. 
Meaning of the word marked with <WSD> tags:  A Schrödinger's cat (a hypothetical cat that may or may not be dead) in particular, especially when implied to be the only Schrödinger's cat in the world.