from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The number thirty in Roman numerals.
- n. Used as an indicator in source code to mark that some work still has to be done.
- n. Traditional brewer's mark for barrels of "extra strong" beer - extended to other alcoholic beverages and other products having an "extra strong" dimension (varying from washing soap to pornography).
- n. An indicator of hazard or poison.
- adj. Extra strong - very high quality
- adj. X-rated, pornographic.
- v. To delete; to edit, especially to conceal or suggest vulgar language.
Very doubtful - although possibly from X, a graphic derivative of the skull and crossbones ("indicator of death") (Wiktionary)