To act recklessly without any scruples or fear of consequences.
肆放肆；忌顾忌；惮害怕。非常放肆，一点没有顾忌。
《礼记·中庸》小人之（反）中庸也，小人而无忌惮也。”
He spent all the company money on luxuries, utterly 肆无忌惮.
Learn the next connected idiom: 肆无忌惮 (sì wú jì dàn) → 担惊受怕 (dān jīng shòu pà)
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