In descriptions of areas in southern Utah, United States, I frequently see mention of slickrock (example from NPS (PDF, 240 KB). However, slickrock is not described on Wikipedia and the first result on Google Search is Join Slickrock for your next Belize (!) vacation. Google Scholar results appear to relate mostly to geographic areas with slickrock or slick rock in the name. Oxford Dictionaries wonders if I meant sly grog (I don't think I do), despite 742,000 results on Google Search and 44,400 on Google Books.
Slick does have several meanings on wiktionary, such as slippery, sophisticated, untrustwothy, clever, great, and smooth. The first and the last make sense in context to rock and consistent with Google Images results, although I can't tell whether slickrock is slippery or not.
What is slickrock?
Best Answer
From Tom McCourt, Cowpokes to Bike Spokes: The Story of Moab, Utah (2007):
The orange, yellow, brown, and white sandstones near Moab, Utah (which is very close to Arches National Park and Canyonlands National Park) are quite grainy—very different in texture from soapstone or marble or other types of rock that might seem better suited for the name slickrock.
In the absence of a better explanation, I would surmise that the both sandiness of the slickrock formations and the lack of firm soil on them to provide good footing contribute to the name. Certainly if ranchers widely used the name generations ago, the particular problems that Tom McCourt says iron-shod horses have with their footing on slickrock are a likely source of the name.