Pronunciation: (pī'ru-sē),[key] —n., —pl.-cies. 1. practice of a pirate; robbery or illegal violence at sea.
2. the unauthorized reproduction or use of a copyrighted book, recording, television program, patented invention, trademarked product, etc.: The record industry is beset with piracy. 3. Also called stream capture.Geol.diversion of the upper part of one stream by the headward growth of another.