direct memory access
Hardware devices attached to PCs (ranging from keyboards to sound cards) can be designed to send their instructions to and from main memory in one of two ways. The default is to ask the CPU to do the work. The more efficient way is to allocate one of the PC's DMA channels to send instructions directly to memory. This leaves the CPU free to do more important things. Like IRQs, DMA channels are limited in number, and you can't allocate one channel to more than one device (unless you want to grind your system to a halt). Most users come in contact with DMA when they install a sound card that--if they're lucky--picks the right channel during setup.
See also: Plug and Play