/ ˈsækrəʊsæŋkt; NAmE -kroʊ-/ adjective
that is considered to be too important to change or question
SYN sacred :
I'll work till late in the evening, but my weekends are sacrosanct.
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WORD ORIGIN
late 15th cent.: from Latin sacrosanctus , from sacro by a sacred rite (ablative of sacrum ) + sanctus holy.