When someone says, "That's my MO," they are referring to their "Modus Operandi," which is a Latin term that translates to "mode of operation" or "method of operation." In English, "MO" is commonly used as an abbreviation for Modus Operandi.
In everyday language, when someone says, "That's my MO," they are talking about their typical way of doing things or their characteristic behavior. It can refer to the habitual approach they take in various situations, whether it's how they handle tasks, solve problems, interact with others, or respond to specific circumstances. Essentially, it's a way of describing their usual pattern or style of behavior.