Sentence:  ... within the hollow crown / That rounds the mortal temples of a king / Keeps Death his court and there the antic sits, / Scoffing his state and grinning at his pomp, / Allowing him a breath, a little scene, / To <WSD>monarchize</WSD>, be fear'd and kill with looks ... 
Meaning of the word marked with <WSD> tags:  To act or play the part of a monarch.