Word Study
geosynclinal
CIDE DICTIONARY
geosynclinal, n. [Gr. ge`a, gh^, the earth + E. synclinal.].
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. [1913 Webster]
For further exploring for "geosynclinal" in Webster Dictionary Online