The word 肆无忌惮 is formed by combining the character 肆, meaning "wanton" or "unrestrained", with 无, meaning "without", and 忌惮, a compound meaning "fear" or "scruple", where 无 negates 忌惮 to emphasize the absence of inhibition, thus creating a phrase that literally means "wanton without fear" and denotes acting recklessly without restraint.