Brown is old blood...however because you say you do suffer from irregular periods, I do suggest a follow up with your gyn. Most of us get brown discharge around the time before and after our periods...so it is normal. However, if you have the discharge throughout your cycle, see your doctor.
I am not an expert on this but I have heard that brown discharge is old blood. It could be dried up from your last period? Or maybe it is just your blood. Sometimes my blood is very dark in color. I mean when I first got my period it was almost black. A friend of mine has irregular periods as well and she has had brown blood like that, she said that it is "old". Drink more water and take vitamins. Talk to your doctor about getting on birth control, perhaps, because maybe regulating your period would help.
Again I am not really sure about this topic, but I have heard of this before and it isn't anything dangerous as far as I know.