Mean-Time-Between-Repair (MTBR)

Similar in meaning to mean time between failures (MTBF), and the two terms are sometimes used interchangeably. 

MTBR is normally quoted for components which are economically viable to repair should they fail. Whereas MTBF is normally quoted for components for which it is not economically viable to repair and which would therefore normally be replaced once they have failed. 

For example a hard disk would not normally be considered repairable should it fail, and thus manufacturers may quote a MTBF figure. W. There will a level of repair where the replaceable entity is not repairable, hence the "R" could be extrapolated to not only mean "repair" but also "replacement". Also starting with MTBF (Mean Time Between Failure, or the time between faults occurring), if the  system under consideration has built-in redundancy then it will not necessarily mean that the system has to be repaired immediately; indeed it may not be possible in say an aircraft. It depends on whether one wishes to use the calculations for the purposes of spares provisioning or resourcing a repair facility; hence BER (Beyond Economic Repair) comes into play.