SAR is an abbreviation for either
Storage Aspect Ratio or
Signal Aspect Ratio. Since one refers to the ratio of vertical to horizontal
Pixels, while the other is based on the shape of a
Frame when displayed it's best not to use this abbreviation except under a few particular circumstances, such as when referring its use in a particular piece of software or hardware. For clarity you can substitute
Display Aspect Ratio (DAR) for
Signal Aspect ratio or just
Aspect Ratio (AR) for
Storage Aspect Ratio.
Related Guides
Resizing DVD-Video To Square Pixels
Digital Video Fundamentals - Resolution and Aspect Ratio
Related Hardware
16:9 HDTVs