Other forms: histrionics; histrionically
Anything that has to do with actors or acting can be called histrionic, like a Broadway actor's histrionic voice projection that would sound strange in everyday life but is perfect for the stage.
The adjective histrionic, pronounced "his-tree-ON-ic," comes from the Latin words histrionicus and histrio which mean “actor.” It can describe things that have to do with acting on the stage, but it can also describe a person who in regular life is a little too dramatic and even over-acts, like your friend whose histrionic rantings make a trip to the grocery store seem like a matter of life and death.