RANDR stands for "Resize and Rotate Extension" and is an official configuration utility to the X Window System extension. It can be used to set the size, orientation, or reflection of the outputs for a screen. It is commonly used for configuring multiple monitors.

Although there are other meanings for the acronym "RANDR," such as "Rest and Relaxation" and "Richmond and Richmond", these meanings are not related to the X Window System extension.

In summary, RANDR is a configuration utility used to set the size, orientation, or reflection of the outputs for a screen in the X Window System extension.