Piracy is a robbery committed at sea, or sometimes on the shore, by an agent without a commission from a sovereign nation. Seaborne piracy against transport vessels remains a significant issue (with estimated worldwide losses of US$13 to $16 billion per year), particularly in the waters between the Pacific and Indian Oceans, off the Somali coast, and in the Strait of Malacca and Singapore, which are used by over 50,000 commercial ships a year. Wikipedia
The definitive Wikipedia entry for Piracy. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Piracy