15世紀初，“在海上搶劫，即在高海上搶劫的行爲”，源自中世紀拉丁語 piratia，源自古典拉丁語、希臘語 peirateia “海盜”，源自 peiratēs “強盜，海盜”（參見 pirate（名詞））。
Specifically, in the law of nations, the crime of depredations or wilful and aggressive destruction of life or property committed on the seas by persons having no commission or authority from any established state. As commonly used it implies something more than a simple theft with violence at sea, and includes something of the idea of general hostility to law. According to the opinion of some, it implies only unlawful interference with a vessel ; according to others, it includes also depredations on the coast by a force landing from the sea. [Century Dictionary]
具體來說，在 aw of nations 中，指的是在海上由沒有任何建立國家的委託或授權的人犯下的掠奪或故意侵犯生命或財產的犯罪行爲。通常使用時，它意味着不僅僅是在海上進行帶有暴力的簡單盜竊，還包含了對法律的普遍敵意的概念。根據一些人的觀點，它僅僅意味着對船隻的非法干擾； 而根據其他人的觀點，它還包括由從海上登陸的武裝力量對海岸的掠奪行爲。[世紀詞典]
