.xxx (pronounced "dot triple-X" or "dot x x x") is a sponsored top-level domain (sTLD) intended as a voluntary option for pornographic sites on the Internet. The sponsoring organization is the International Foundation for Online Responsibility (IFFOR). The registry is operated by ICM Registry LLC. The ICANN Board voted to approve the sTLD on 18 March 2011. It went into operation on 15 April 2011.
Noun 1. the cardinal number that is the product of ten and three (synonym) thirty, 30 (hypernym) large integer 2. (genetics) abnormal complement of three X chromosomes in a female (hypernym) sex chromosome (classification) genetics, genetic science Adjective 1. being ten more than twenty (synonym) thirty, 30 (similar) cardinal
/X-X-X/ n. A marker that attention is needed. Commonly used in program comments to indicate areas that are kluged up or need to be. Some hackers liken `XXX' to the notional heavy-porn movie rating. Compare FIXME.