What does the abbreviation RR HTD IND mean on a fuse box diagram inside an automibile?

That abbreviation likely refers to Rear Right High-Tension Discharge Indicator. It's indicating a fuse protecting a circuit related to a high-voltage component in the rear right of the vehicle. This is most likely associated with modern vehicles that have high voltage systems for hybrid or electric components. The "indicator" part means the fuse protects a circuit that shows a warning light or other indication to the driver about that component's status.