For a class of feedforward nonlinear systems, we systematically solve the global adaptive stabilization problem. The proposed adaptive stabilizer consists of a nested saturation feedback and a tuning mechanism, which is constituted by a set of switching logics and is used to adaptively tune the saturation levels in a switching manner. It is proved that under the proposed control, global asymptotic regulation of states is achieved. The class of systems can be of arbitrary dynamic order, the contained uncertain nonlinearities need not be explicitly bounded, and even the form of nonlinearities can also be unknown.