Munkers = Any Junker with 2+ Minelaunchers.
Why not just 1 mine? Because while 1 mine is good enough to keep an enemy at bay, the boat will most likely use it's side guns more. How you fly the vessel changes very little. The mine launcher is only there for defensive purposes. When you add a 2nd mine launcher, you add the ability to easily fend off multiple vessels as well as use mines more effectively in an offensive manner instead of just defense. While you may have a kill side or disable side, your piloting style changes as you can approach engagements differently. When your piloting style shifts, thats called Munker.