from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A usually elongate, basinlike depression along the edge of a continent, in which a thick sequence of sediments and volcanic deposits has accumulated.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A large, linear depression in the Earth's crust in which sediment accumulates.
from The Century Dictionary and Cyclopedia
- n. In geology, a considerable tract in which the strata are bent into a great trough with many minor undulations on the flanks.
Back-formation from geosynclinal. (Wiktionary)