from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A polished, striated rock surface caused by one rock mass sliding over another in a fault plane.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A smooth, striated rock surface caused by the friction of one mass sliding over another
Dialectal slicken, glossy (alteration of slick) + side.(American Heritage® Dictionary of the English Language, Fourth Edition)