modus operandi
A unique and habitual method of doing something. From Latin, literally "mode of operation." Used especially in reference to criminal behavior. OK, this guy's modus operandi is breaking into houses completely at random and not taking anything. So then what's his motive? Most serial killers have a modus operandi of some sort. If we can determine that, then we may be able to stop this maniac.
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.