XXX

From Wiktionary

Numeral[change]

  1. The number thirty (30) in Roman numerals.

Symbol[change]

  1. (coding) A placeholder to mark a place where work still needs to be done.
  2. A mark placed on containers of alcoholic beverages that means it is especially strong.
    1. By extension, XXX is a mark put on anything that is especially strong or potent. It is most notably used to refer to hardcore pornography and even to just refer to pornography in general.
  3. An indicator of hazard or poison.