Sentence:  In October, an anonymous 4chan account began making cryptic posts about earth-changing political and judicial events to come. Ever since then, conspiracy theorists, journalists, and amused observers have speculated about who was behind the account that has come to be known as <WSD>QAnon</WSD>. 
Meaning of the word marked with <WSD> tags:  An anonymous poster on 4chan and 8chan, claiming to possess Q clearance and also known as Q, who originated a pro-Trump conspiracy theory that (Donald Trump) secretly cooperates with (Mueller's Special Counsel investigation) to prosecute prominent Democrats.