period when a system is unavailable

DOWNTIME
List of words for the clue period when a system is unavailable from the crossword:
INUSE ERA OUT NOTIN EON TIEUP TIEDUP TAKEN INTRUST INAVAILABLE ICICLE ICANT ELEC DRYUP COPY BUSY BLT LENT EPOCH
WordClue
AGEera, period
ERAperiod, epoch
NAPshort period of sleep
LULLperiod of rest
SALLYWhen Harry Met ... (film)
FREEZEperiod of intensely cold weather
SEASONinterval, period
INFANCYperiod of childhood
PERMIANgeologic period
CAMBRIANgeologic period
DEVONIANgeologic period
INTERVALperiod, pause
JURASSICgeologic period
SILURIANgeologic period
TIMESPANperiod
TRIASSICgeologic period
PALEOGENEgeologic period
CRETACEOUSgeologic period
ORDOVICIANgeologic period
CARBONIFEROUSgeologic period
INTERVALperiod, pause
VISIONperipheral or stereoscopic