A modus operandi is someone's habits of working, particularly in the context of business or criminal investigations; but also more generally, it is a Latin phrase, approximately translated as mode of operating.

What does M.O. mean slang?

The acronym MO is short for modus operandi, an expression directly from Latin meaning “way of operating.” Modus operandi was first recorded in English by the 1650s. The phrase specifically refers to the particular, often characteristic manner someone goes about doing something—later broadened to one's “style.”

What does M.O. stand for in crime?

Primary tabs. A Latin phrase meaning “mode of operating.” In criminal law, modus operandi refers to a method of operation or pattern of criminal behavior so distinctive that separate crimes or wrongful conduct are recognized as the work of the same person.