Daily Chinese Idiom Guessing Game
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.