1. robbery committed at sea.
2. A similar act of robbery, as the hijacking of an airplane.
3. the unauthorized use or reproduction of copyrighted or patented material: software piracy.
4. the operation of an unlicensed, illegal radio or television station.

1. robbery at sea, a violation of international law; taking a ship away from the control of those who are legally entitled to it.
2. A similar violation of international law, such as hijacking of an aircraft.
3. the unauthorized duplication of goods protected by intellectual property law (e.g. copying software unlawfully).
4. the operation of an unlicensed radio or television station.

1. the act or crime of a pirate.
2. robbery on the high seas; the taking of property from others on the open sea by open violence; without lawful authority, and with intent to steal; -- a crime answering to robbery on land.
3.

1. robbery upon the sea; robbery by pirates; the practice of robbing on the high seas.
2. literary theft; any unauthorized appropriation of the mental or artistic conceptions or productions of another; specifically, an infringement of the law of copyright.
3. in geology, that process whereby, because of a higher natural gradient, and therefore more efficient eroding power, one stream cuts back a divide and taps off the head-waters or a tributary of another stream. the captured stream usually turns a sharp angle into its new course and leaves a wind-gap where it formerly flowed. also called stream-piracy.

1. hijacking on the high seas or in similar contexts; taking a ship or plane away from the control of those who are legally entitled to it
2. the act of plagiarizing; taking someone's words or ideas as if they were your own