Many words are used and they mean different things for different people. But words such as Immutable, Absolute, Transcendental are used by Buddhist teachers of all varieties: Zen, Mahayana, and Theravada. A few samples.
http://selfdefinition.org/zen/Zen-and-Dzogchen--12-page-article.pdf
Thus, Absolute or Ultimate Truth—shunyata—is both origin and aim. While the gradualist path of the Hinayana and the Mahayana uses prajna, the Inner Tantras, and especially the Ati Yoga of Dzogchen, utilise the non-coneptual, nondual innate primordial wisdom (sahajajnana, yeshe, gnosis) the natural luminosity of essential mind nature. This blissful intuitive wisdom cannot be grasped by discursive, conceptual analytic meditation (prajna). It can only be directly realised (pratyaksa), suddenly, through transmission and empowerment by the master. It is then brought to fruition by nondual meditation under the guidance of the master. The primordial wisdom is the Buddha Nature, the tathagatagarbha,.......
http://buddhism.about.com/od/mahayanabuddhism/a/aboutmahayana.htm
Connected to sunyata is the teaching that Buddha Nature is the immutable nature of all beings....
Very simply, dharmakaya is the body of absolute truth,....
http://www.thezensite.com/ZenEssays/Philosophical/Absolute_in_Chan.htm
The Womb of Tathaagata spoken by the Buddha means aalayavij~naana; however, those of defective knowledge do not understand that the Womb is the aalayavij~naana. The relationship between the pure Womb of Tathaagata and the worldly aalayavij~naana resembles gold and its productions such as finger-rings; the characteristics might be different, yet [the substance] is not.(30)
http://www.budsas.org/ebud/ebdha135.htm
Buddhism has been a religion of practices than of grace. It changed from the radical pluralism of Hinayana to the absolutism of the Mahayana. There was felt the need for a mediating principle between the absolute and phenomenal being. Buddha is that mediator. In Prajnaparamita, as non-dual knowledge, it is equated with Tathagata and as prajna he is identical with the absolute; but as a human being subjecting himself to all limitations, he is at once phenomenal. Relation of the Tathagata to the Absolute (prajna-sunyata) is one sided; the former depends on the latter, and not vice verse.
The late Tibetan master Kalu Rinpoche said: "You live in illusion and the appearance of things. There is reality, you are that reality. When you understand this, you will see that you are nothing. And being nothing, you are everything. That is all."
http://selfdefinition.org/zen/Zen-and-Dzogchen--12-page-article.pdf
Thus, Absolute or Ultimate Truth—shunyata—is both origin and aim. While the gradualist path of the Hinayana and the Mahayana uses prajna, the Inner Tantras, and especially the Ati Yoga of Dzogchen, utilise the non-coneptual, nondual innate primordial wisdom (sahajajnana, yeshe, gnosis) the natural luminosity of essential mind nature. This blissful intuitive wisdom cannot be grasped by discursive, conceptual analytic meditation (prajna). It can only be directly realised (pratyaksa), suddenly, through transmission and empowerment by the master. It is then brought to fruition by nondual meditation under the guidance of the master. The primordial wisdom is the Buddha Nature, the tathagatagarbha,.......
http://buddhism.about.com/od/mahayanabuddhism/a/aboutmahayana.htm
Connected to sunyata is the teaching that Buddha Nature is the immutable nature of all beings....
Very simply, dharmakaya is the body of absolute truth,....
http://www.thezensite.com/ZenEssays/Philosophical/Absolute_in_Chan.htm
The Womb of Tathaagata spoken by the Buddha means aalayavij~naana; however, those of defective knowledge do not understand that the Womb is the aalayavij~naana. The relationship between the pure Womb of Tathaagata and the worldly aalayavij~naana resembles gold and its productions such as finger-rings; the characteristics might be different, yet [the substance] is not.(30)
http://www.budsas.org/ebud/ebdha135.htm
Buddhism has been a religion of practices than of grace. It changed from the radical pluralism of Hinayana to the absolutism of the Mahayana. There was felt the need for a mediating principle between the absolute and phenomenal being. Buddha is that mediator. In Prajnaparamita, as non-dual knowledge, it is equated with Tathagata and as prajna he is identical with the absolute; but as a human being subjecting himself to all limitations, he is at once phenomenal. Relation of the Tathagata to the Absolute (prajna-sunyata) is one sided; the former depends on the latter, and not vice verse.
The late Tibetan master Kalu Rinpoche said: "You live in illusion and the appearance of things. There is reality, you are that reality. When you understand this, you will see that you are nothing. And being nothing, you are everything. That is all."