Modus operandi (often used in the abbreviated forms M.O. or simply Method) is a Latin phrase, approximately translated as "method of operating" The term is used in English to describe someone's habits or manner of working, the method of operating or functioning. It is often used in a criminal sense, to profile the methods employed by individuals during the execution of a crime, and may also be used in offender profiling,2 where it can also be used to find clues to the perpetrator's psychology.3 It largely consists of the methods used to execute the crime, prevent detection, and facilitate escape.

stands for modus operandi which translates as method of operation

slang that means a lot or in an excessive amount.

short for "modus operandi"...a person's way of doing things or their style.

Short for homo. Mainly used by the gay community when referring to each other. Rarely used as a homophobic insult.

Abbreviation in both speech and text for "<i>modus operandi</i>" (Latin) or "mode of operation" (English). The term is used to mean either the way in which one does something, or his or her focus or goal/ambition in a certain aspect of life.

"Main Entry:
mo·dus ope·ran·di
Pronunciation:
\ˌmō-dəs-ˌä-pə-ˈran-dē, -ˌdī\
Function:
noun
Inflected Form(s):
plural mo·di operandi \ˈmō-ˌdē-, ˈmō-ˌdī-\
Etymology:
New Latin
Date:
1654

: a method of procedure ; especially : a distinct pattern or method of operation that indicates or suggests the work of a single criminal in more than one crime"

Straight from Merriam-Webster, folks. http://www.merriam-webster.com/dictionary/modus+operandi

The idiot that said, "<i>operandi</i> is not a Latin word" is incorrect and needs more thumbs down. That entry should be removed.

M O is an abbreviation for Modus Operandi. which is Latin for Method of Operation or Mode of Operation

In criminal investigations, it refers to the criminal's methods whether murder or burglary or whatever as similar methods used in separate offences which could indicate the same person was responsible.

It doesn't have to pertain to crime. It can also be used to describe a person's 'trade mark' habits.