Sentence:  A <WSD>specter</WSD> is haunting Europe — the <WSD>specter</WSD> of communism. All the powers of old Europe have entered into a holy alliance to exorcise this <WSD>specter</WSD>: Pope and Tsar, Metternich and Guizot, French Radicals and German police-spies. 
Meaning of the word marked with <WSD> tags:  A threatening mental image.