This prophecy talks about a time yet future where anyone who stands for the bible will be executed by beheading. What form that will take is not entirely certain, and some believe it'll be by guillotine, as that would be the fastest, "mass production" method of execution of achieving this task. But it could also be as simple as a knife and lots of sawing as seen being used by ISIS. Either way, this is the form of martyrdom that believers during the Tribulation will have to face.
(*Do you have a better description, or did you find an error? Please let me know.