Have never heard of under ground gambling and if I am not mistakenly this could be applied to the country where they sees gambling as an illegal activities or is totally prohibited From gambling. As I know, my country doesn't prohibited gambling rather anyone gambling should gamble responsibly. Between my first time of hearing there is an underground gambling where people goes to gamble without the knowledge of their State or government authority to know about this type of place except you were called and gives a direction to come such place to gamble.