Scatter-gather
A transfer that reads from or writes to several separate memory regions in one go, instead of copying them into one place first.
A basic DMA channel can only move one contiguous block. With scatter-gather it is handed a list of descriptors — address and length for each piece — and works through them in order without the CPU having to wake up in between. Gather collects from many places on transmit; scatter spreads out on receive.
Network cards are the canonical example: the protocol header sits in one buffer, the payload in another, and the card reads both directly. The same idea exists in software as readv() and writev(), introduced in 4.2BSD. In firmware it is often combined with a ring of descriptors that the DMA controller laps around indefinitely.