See "completely impenetrable". 

The canonical use of this phrase is seen when working on difficult math problems. Work backward from the result, and forward from the problem. If you can't get anywhere with either approach, then insert "It is intuitively obvious that" between the two.

It's another way of saying ThenaMiracleOccurs.

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When used with a guy I used to work with, the phrase was "Read the code, it's intuitive."

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''I had a professor who would abbreviate the phrase to M.O.  Of course, the material in question had been proven; he just didn't care to present the proof to a lecture hall full of undergraduates who wouldn't have understood it anyway.''

I had a professor with a memorable and apparently unintentional turn of phrase. One particularly fine example was "It is obvious that this is not obvious" (he was right, too).
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See also TrivialTask