Modus operandi

method of operation, manner of action

Modus operandi (often used in the abbreviated forms MO, M.O. or simply Method) is a Latin phrase, approximately translated as "mode of operation". The plural is modi operandi ("modes of operation"). It is used in law enforcement to describe a criminal's characteristic patterns and style of committing crimes. It is also applied in fraud investigation when talking about behavior patterns that indicate specific types of fraud, e.g., "False identity is a key MO of retail banking sleeper fraud".
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Noun
1. an unvarying or habitual method of procedure
(synonym) routine
(hypernym) procedure, process
(hyponym) rat race

modus operandi, method of operation, manner of action

the standard operating procedure.