/ ˌkɑːt ˈblɑːnʃ; NAmE ˌkɑːrt/ noun
[ U ] (from French ) carte blanche (to do sth) the complete freedom or authority to do whatever you like
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WORD ORIGIN
late 17th cent.: French , literally blank paper (i.e. a blank sheet on which to write whatever one wishes, particularly one's own terms for an agreement).