Geosynclinal \Ge`o*syn*cli"nal\, n. [Gr. ge`a, gh^, the earth +
E. synclinal.] (Geol.)
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]