Let me first begin by defining through example: ALL YOUR BASE ARE BELONG TO US!!
Janglish is what you get when you take Japanese and transliterate it (often poorly) into English. Or, when you take an English word or phrase say, "super market," Japanify it into, "suupaa," and then try and then hear some anime freak use it in an English sentence, "We suupaa go!!" Damn the otaku, damn them!
Can You Provide an Example?
On my Japanese exams in college, my well-intentioned Japanese professor would often provide the phrases we were supposed to translate into Japanese in Janglish to make it "easier" for us to understand exactly how she would want the phrases translated. This made our job more like transliterating, so I guess in retrospect it was easier. Here is a real-life example from a test:
It is that the computer has become not fast.
I simply cannot make that up. Silly that not is?
But Why Call it Janglish?
Well in Korea, they actually call this sort of thing Chonglish; so it makes sense to just shift the whole concept over a nation. Agree you do not?