What is the X in X-mas?
The way someone does something; a characteristic method: “Her modus operandi in buying a new car always included a month of research.” This phrase, often abbreviated “m.o.,” is used by police to describe a criminal's characteristic way of committing a crime. From Latin, meaning “method of operation.”
in criminology, distinct pattern or manner of working that comes to be associated with a particular criminal. Criminologists have observed that, whatever his specialty-burglary, auto theft, or embezzling-the professional criminal is very likely to adhere to his particular way of operating. If, for example, a burglar begins his career by entering houses from the roof, he will, in all probability, continue this method for as long as he is able to work. Some burglars become so attached to their modus operandi that they burglarize the same places or people again and again.