What is Reprisal?

Legal Definition
A reprisal is a limited and deliberate violation of international law to punish another sovereign state that has already broken them. Reprisals in the laws of war are extremely limited, as they commonly breached the rights of non-combatants, an action outlawed by the Geneva Conventions. It is not to be confused with retorsions, as these constitute unfriendly acts generally permitted by international law.
-- Wikipedia
Legal Definition
War. The forcibly taking a thing by one nation which belonged to another, in return or satisfaction for a injury committed by the latter on the former. Vatt. B., 2, ch. 18, s. 342; 1 Bl. Com. ch. 7.

2. Reprisals are used between nation and nation to do themselves justice, when they cannot otherwise obtain it. Congress have the power to grant letters of marque (q. v.) and reprisal. Const. art. 1, s. 8 cl. 11.

3. Reprisals are made in two ways either by embargo, in which case the act is that of the state; or, by letters of marque and reprisals, in which case the act is that of the citizen, authorized by the government. Vide 2 Bro. Civ. Law, 334.

4. Reprisals are divided into negative, when a nation refuses to fulfil a perfect obligation, which it has contracted, or to permit another state to enjoy a right which it justly claims; or positive, when they consist in seizing the persons and effects belonging to the other nation, in order to obtain satisfaction.

5. They are also general or special. They are general when a state which has received, or supposes it has received an injury from another nation delivers commissions to its officers and subjects to take the persons and property belonging to the other nation, in retaliation for such acts, wherever they may be found. It usually amounts to a declaration of war. Specia reprisals are such as are granted in times of peace, to particular individuals who have suffered an injury from the citizens or subjects of the other nation. Bynker. Quaest. Jur. Pub. lib. 1, Duponce, au's Translation, p. 182, note; Dall. Diet. Prises maritimes, axt. 2, §5.

6. The property seized in making reprisals is preserved, while there is any hope of obtaining satisfaction or justice, as soon as that hope disappears, it is confiscated, and then the reprisal is complete. Vattel, B. 2, c. 18, §342.
-- Bouviers Law Dictionary
Legal Definition
The forcibly taking a thing by one nation which belonged to another, in return or satisfaction for an injury committed by the latter on the former. Vattel, b. 2, c. 18, s. 342.
-- Black's Law Dictionary
Legal Definition
a retaliation against a wrongful actor an unfriendly act.
Legal Definition
-- Ballentine's Law Dictionary