Finally, though, I thought of one! (Well, actually I though of two others, but I won't digress... ha! Oh, and at least two other great words have already been used: mylonite and welded tuff.)
The word: Detachment, more specifically Detachment Fault. The entire post envisioned a couple nights ago, "Detachment: See header photo." (That's the one up there, above this blog post.)
I have gone a little beyond that short, terse post, but won't really get into a definition, which would involve a low-angle normal fault of regional extent, probably created by, or during a period of, what is sometimes known as "extreme extension."
Official AGI definition for detachment fault.
Detachment Fault: a good geological mystery book.
A number of Detachment Quotes.
My posts labeled "detachment" (there are only 20 so far, including this one).
Detachment fault on Facebook (it has no friends!)
The Northern Snake Range décollement or detachment fault as seen from Great Basin National Park.
This post has been submitted to Accretionary Wedge #35: What's Your Favorite Geology Word?