The fact that ones using Ni as dominant can't explain Ni seems ironic, but it's actually true: we are so familiar with it that we don't even find the necessity to verbalise the thought processes. Anyway, I was interested in Ni a lot, and I did my own research about it.
What I didn't like about most Ni descriptions is that they think Ni works without any contextual data. Little external stimuli are required, that's true, but without any contextual data is *not* true, because Ni is strictly a *perceiving* function. I hated the descriptions that relate Ni with being mystical.
Some of my definitions of Ni - never mind, it's not really definition, explanation with examples:
I.
"Ah, all the details are falling into the right place, with that 'aha' moment": you digest concepts globally via your subconscious. Let the subconscious dissect the complex concepts as they permeate through your brain. When you get the "aha" moment you know the details of concepts and ideas fall into the place - into the "just right" place.
II.
"Meditative Daydreaming": I think this has been sufficiently discuss in this thread, so I will pass this.
III.
"'I-just-know-and-it-demands-an-action' forecasting": without knowing much about departments, I chose to apply one of the colleges based on this vague yet powerful "long-range-forecasting." Surprisingly, amongst the top 3 schools I wanted to attend, this was the only one that accepted me.
IV.
"Let's look at something in different perspectives": This is connected to INxJ's strongly individualistic sets of beliefs. Ni urges them to perceive their experiences in different (if possible, all-encompassing. Lenore talks about this.) perspectives. With this, you will get to acknowledge different views (Satya talked about this in the thread about the INFJ-and-INFP differences); I also believe, however, this is the sources of symbolism.
V.
Vicky Jo's description of Introverted Intuition:
http://infj.com/INFJ_iNtuition.htm
She equated Ne with "divergent" perceiving process (take-off), and Ni with "convergent" thinking process (landing). Interesting description.