From Rangjung Yeshe Wiki - Dharma Dictionnary
Shamatha (zhi gnas). Stillness, literally 'calm abiding' or 'remaining in quiescence' after thought activity has subsided. It can also mean the meditative practice of calming the mind in order to rest free from the disturbance of thought.
- Shamatha with support (zhi gnas rten bcas) is the practice of calming the mind while using an object of concentration, material or mental, or simply the breath.
- Shamatha without support (zhi gnas rten med) is the act of calming the mind without any particular object, resting undistractedly. This practice serves as a prelude for Mahamudra and Dzogchen and should not be mistaken for 'ordinary mind', tha mal gyi shes pa, or the view of Trekchö.[RY]