Samyama (from Sanskrit संयम saṃ-yama—holding together, tying up, binding). Combined simultaneous practice of Dhāraṇā (concentration), Dhyāna (meditation) & Samādhi (union). A tool to receive deeper knowledge of qualities of the object. It is a term summarizing the "catch-all" process of psychological absorption in the object of meditation.
Samyama, as Patanjali's Yoga Sutras states, engenders prajñā. Adi Yoga or Mahasandhi discusses the 'mūla prajñā' of "listening/studying, investigation/contemplation, realization/meditation" which are a transposition of the triune of Samyama. These are activated subconsciously in non-structured form (thus producing fragmented spontaneous Samyama-like effects) by any thinking activity or contemplative absorption (particularly the Catuskoti and Koan) and deep levels of trance. Any kind of intuitive thinking at its various stages of expression is strongly related to Samyama-like phenomena as well.
Samyama is practiced consistently by Yogin of certain schools (Raja Yoga, Adi Yoga e.g.). Described in Yoga Sutras of Patanjali, it comprises the three upper limbs of Raja Yoga. Following Patanjali's Yoga Sutras, a yogin who is victorious in samyama vanquishes all 'cognitive obscurations' (Sanskrit: klesha). The Sutras describe various 'powers' or 'perfections' (Sanskrit: siddhi) a yogin may attain through the conduit of Samyama.
Yoga Sutras 
|Pada (Chapter)||English meaning||Sutras|
|Samadhi Pada||On being absorbed in spirit||
|Sadhana Pada||On being immersed in spirit||
|Vibhuti Pada||On supernatural abilities and gifts||
|Kaivalya Pada||On absolute freedom||
Samyama is defined in the Yoga Sutras of Patanjali verses 3.1 through 3.6 as follows where the Sanskrit in Devanagari and IAST were sourced from Little and the English from Iyengar (1993: pp. 178–183):
देशबन्धश्चित्तस्य धारणा ॥ १॥
deśabandhaścittasya dhāraṇā .. 1..
Fixing the consciousness on one point or region is concentration (dhāraṇā).
तत्र प्रत्ययैकतानता ध्यानम् ॥ २॥
tatra pratyayaikatānatā dhyānam .. 2..
A steady, continuous flow of attention directed towards the same point or region is meditation (dhyāna).
तद् एवार्थमात्रनिर्भासं स्वरूपशून्यम् इव समाधिः ॥ ३॥
tad evārthamātranirbhāsaṃ svarūpaśūnyam iva samādhiḥ .. 3..
When the object of meditation engulfs the meditator, appearing as the subject, self-awareness is lost. This is samādhi.
त्रयम् एकत्र संयमः ॥ ४॥
trayam ekatra saṃyamaḥ .. 4..
These three together [dhāraṇā, dhyāna and samādhi] constitute integration or saṃyama.
तज्जयात् प्रज्ञालोकः ॥ ५॥
tajjayāt prajñālokaḥ .. 5..
From mastery of saṃyama comes the light of awareness and insight.
तस्य भूमिषु विनियोगः ॥ ६॥
tasya bhūmiṣu viniyogaḥ .. 6..
Saṃyama may be applied in various spheres to derive its usefulness.
See also 
Samyama can be done on different objects.
- Sanskrit-English Dictionary by Monier-Williams, (c) 1899
- Sansonese, J. Nigro (1994). The Body of Myth: Mythology, Shamanic Trance, and the Sacred Geography of the Body. Inner Traditions. ISBN 978-0-89281-409-1. Source: Google Books (accessed: Friday March 6, 2009), p.26.
- Patanjali's Yoga Aphorisms: Powers, Ramakrishnavivekananda.info
- Yoga, Agency for Healthcare Research and Quality, U.S. Department of Health and Human Services.
- Learntm.com, Yoga Sutras: Description of TM-Sidhi Program.
- Stiles 2001, p. x.
- Little, Alan (n.d.). The Yoga Sutras of Patanjali. Source: Alanlittle.org (accessed: Wednesday March 17, 2010)
- Iyengar, B.K.S. (1993). Light on the Yoga Sutras of Patanjali. Hammersmith, London, UK: Thorstons (an imprint of HarperCollinsPublishers). ISBN 978-0-00-714516-4, pp.178-183.