Cascading of quad poles, components or connections means their stringing together.
In Ethernet, cascading is the connection of two stations across several repeaters. In internetworking, cascading is connecting stations across multiple networks. And in filters, it is the stringing together of filters to create higher orderfilters. By cascading several filters, one can increase the slope and adapt it to the requirements.
The cascading of amplifiers is about the stringing together of amplifiers. The amplifier output of one amplifier is connected to the amplifier input of the next amplifier. This forms an amplifier chain with which the total gain is increased.