Isolation cells and humiliation... well, I guess it depends on degree, but I think most definitions of "torture" would include some degree of those methods. Unless the definition is by Bush & Co, or other NeoCons, etc., then it can mean whatever they want it to mean, or not mean, as the case may be.

Some definitions:

1 a: anguish of body or mind : agony b: something that causes agony or pain
2: the infliction of intense pain (as from burning, crushing, or wounding) to punish, coerce, or afford sadistic pleasure
3: distortion or overrefinement of a meaning or an argument.

Merriam-Webster Online

Torture: An act by which severe pain or suffering, whether physical or mental, is intentionally inflicted on a person, for a purpose such as obtaining information or a confession, punishment, intimidation or coercion, or for any reason based on discrimination of any kind. Survivors of torture often suffer from physical and psychological symptoms and disabilities. There may be specific forms of physical injury including broken bones, neurological damage, and musculoskeletal problems. Torture may result in psychological symptoms of depression (most common), post-traumatic stress disorder, marked sleep disturbances and alterations in self-perceptions together with feelings of powerlessness, fear, guilt and shame.

MedicineNet

The 1984 United Nations Convention Against Torture (Article 1) provides a definition of torture that is considered customary.

International humanitarian law (IHL) differs somewhat from this definition in not requiring the involvement of a person acting in an official capacity as a condition for an act intended to inflict severe pain or suffering to be defined as torture.

The ICRC uses the broad term "ill-treatment" to cover both torture and other methods of abuse prohibited by international law, including inhuman, cruel, humiliating, and degrading treatment, outrages upon personal dignity and physical or moral coercion.

The legal difference between torture and other forms of ill treatment lies in the level of severity of pain or suffering imposed. In addition, torture requires the existence of a specific purpose behind the act – to obtain information, for example.

The various terms used to refer to different forms of ill treatment or infliction of pain can be explained as follows:

* Torture: existence of a specific purpose plus intentional infliction of severe suffering or pain;

* Cruel or inhuman treatment: no specific purpose, significant level of suffering or pain inflicted;

* Outrages upon personal dignity: no specific purpose, significant level of humiliation or degradation.

Methods of ill treatment may be both physical and/or psychological in nature and both methods may have physical and psychological effects.

International Committee of the Red Cross

1. For the purposes of this Convention, the term "torture" means any act by which severe pain or suffering, whether physical or mental, is intentionally inflicted on a person for such purposes as obtaining from him or a third person information or a confession, punishing him for an act he or a third person has committed or is suspected of having committed, or intimidating or coercing him or a third person, or for any reason based on discrimination of any kind, when such pain or suffering is inflicted by or at the instigation of or with the consent or acquiescence of a public official or other person acting in an official capacity. It does not include pain or suffering arising only from, inherent in or incidental to lawful sanctions.

UN High Commisioner for Human Rights

The above signed and ratified by the USA.

I particularly like part 3 of the Merriam Webster definition.