Decapitates is a verb that means to cut someone's head off. Some synonyms for this word include beheading, guillotining, executing, slaughtering, and killing. To behead someone means to cut off their head, usually as a form of execution. Guillotining refers to the act of using a guillotine, which is a machine designed to behead a person by dropping a blade onto their neck. Executing means causing someone to be put to death, usually by legal means. Slaughtering means killing animals or people on a large scale, often in a brutal or violent way. Lastly, killing means taking someone's life, regardless of the method used.