/ ɪkˈstenjueɪtɪŋ; NAmE / adjective
[ only before noun ] ( formal ) showing reasons why a wrong or illegal act, or a bad situation, should be judged less seriously or excused :
There were extenuating circumstances and the defendant did not receive a prison sentence.
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WORD ORIGIN
late Middle English (in the sense make thin ): from Latin extenuat- made thin, from the verb extenuare (based on tenuis thin) + -ing .