A term invented by angry atheists who suffer from anger management issues and superiority complex. It is a portmanteau of 'pugnacious' and 'atheism', although it is often mistakenly referred to as a contraction instead of a portmanteau, which should give some indication of the overall intelligence of those who say they practice it. The term means aggressive atheism, and is characterized by thinking oneself to be automatically superior to anyone who believes in any kind of religion, and feeling that it's necessary to verbally abuse such people. This is the opposite of using a "live and let live" attitude, and so they refuse to be tolerant of the life choices of others, even when those others are tolerant of the life choice of the atheist.
Hobbies of those who practice pugnatheism include, but are not limited to: making sweeping over-generalizations about various persons, groups, organizations, and even who geographic regions; complete and utter refusal to be tolerant of anyone whose beliefs or philosophies differ from your own; angrily arguing on internet forums with religious people in order to tell them how wrong and stupid they are instead of simply living your life enjoyably and letting them do the same; believing yourself to be such a brilliant genius that you know the exact nature of the universe and calculate with 100% accuracy that there couldn't possibly be anything besides what you can see with your own two eyes; and of course, practicing regular worship of Richard Dawkins.