Cnmdb is the abbrevation for "cao ni ma de bi" and it means "fuck your mother's vagina" in Chinese. Chinese often use it to expressfrustration and dissatisfaction.
This is a typical Chinese slang, which is the initials for “cào nǐ mā bī” which means fuck ur mom’s vagina. Often used in curses for online/real life arguments.
Acronym of the Chinese swear "Cao Ni Ma Bi". Literally it translates to "Fuck Your Mother's Pussy", which means (I) (will)/(want) fuck your mother or I'm your dad.
Unlike the English word of "motherfucker", which suggests incest of the object person, an user of "CNMB" shames others by flaunting itself as a (powerful) rapist/conqueror.