The precise definition varies by jurisdiction, but typically includes punishments that are arbitrary, unnecessary, or overly severe compared to the crime.
Very similar words, "No one shall be subjected to torture or to cruel, inhuman or degrading treatment or punishment", appear in Article 5 of the Universal Declaration of Human Rights adopted by the United Nations General Assembly on December 10, 1948.
[3] The Constitution of the Marshall Islands, in the sixth section of its Bill of Rights (Article 2), prohibits "cruel and unusual punishment", which it defines as: the death penalty; torture; "inhuman and degrading treatment"; and "excessive fines or deprivations".
The general principles that the United States Supreme Court relied on to decide whether or not a particular punishment was cruel and unusual were determined by Justice William Brennan.
And he added: "The function of these principles, after all, is simply to provide [the] means by which a court can determine whether [the] challenged punishment comports with human dignity.