Geosynclinal :: Geosynclinal (n.) the downward bend or subsidence of the earth's crust, which allows of the gradual accumulation of sediment, and hence forms the first step in the making of a mountain range; -- opposed to geanticlinal..
Synclinal :: Synclastic (a.) Curved toward the same side in all directions; -- said of surfaces which in all directions around any point bend away from a tangent plane toward the same side, as the surface of a sphere; -- opposed to anticlastic..
Synclinal :: Synclinal (a.) Inclined downward from opposite directions, so as to meet in a common point or line..
Synclinal :: Synclinal (a.) Formed by strata dipping toward a common line or plane; as, a synclinal trough or valley; a synclinal fold; -- opposed to anticlinal..