Full-scene anti-aliasing is a system being adopted by the latest generation of 3D graphics chip manufacturers to offer a better quality image in 3D computer games. It is independent of the graphics API being used (DirectX or OpenGL, mainly) and so you won't have to wait for games to start supporting it.

Simply put, its the same as anti-aliasing (smoothing out the 'jaggies' that appear as lines and edges are drawn on a computer screen), but generally anti-aliasing is used in reference to edge anti-aliasing, whereas full-scene anti-aliasing is indicative of the anti-aliasing of each frame of a 3D scene drawn on the screen by the video card.

Full-scene anti-aliasing in mainstream 3D graphics cards is available on any graphics card newer than the 3dfx Voodoo5 or NVIDIA GeForce2 GTS, both of which were current in 1999-2000. NVIDIA also has drivers, FSAA, which can be enabled on their GeForce 256 cards too (I've heard that it works on the TNT2 as well, but it never worked on my TNT2U) via software, but the image quality wasn't too impressive to me on mine, and it really was slow.