"Sniglet" isn't in the dictionary

We were suprised to find (logical difficulties notwithstanding) that the Shorter Oxford English Dictionary (which is also available on CD-ROM for computers) doesn't contain the word "sniglet."

Our favorite sniglet is prndl, which coincidentally is a transportation related term.

Question: How was Devil's Slide formed?

From: ypcopy1001@qwest.net

How was Devil's Slide formed? Corrosion, Earthquake, Mudslide, or Floods? Cannot find it anywhere.