Definition: "mpl4" refers to the first four letters of a word, which are "M", "p", "l", and "4". The word "military police" could be formed with these characters. Definition: "mpl4" is used in context to refer to the military police department, which is an agency within a state's military force. This term can also describe a group of soldiers, commonly used in a military setting to represent them as part of their unit or a larger organization. For example, if you were writing about an army, "mpl4" could be used to denote the military police division of that unit.