The Free On-line Dictionary of Computing (30 December 2018):

fault tolerance
fault tolerant
FT

    1. The ability of a system or component to
   continue normal operation despite the presence of hardware or
   software faults.  This often involves some degree of
   redundancy.

   2. The number of faults a system or component can withstand
   before normal operation is impaired.

   (1995-04-06)