Comparative to the term Half-ass, although this is only used in church settings. A half Masser will leave Mass early because they feel that their time is too important to waste on staying the entire mass. The most common time to spot a Half-Masser is right before or during the final hymn of the mass, because they want to miss out on
the massive cluster fuck that occurs in the
parking lot immediate following Mass.
Half Massers are only above people who attend Mass once a year in terms of how much they are hated in the religious society.