Patañjali (Sanskrit: पतञ्जलि, IPA: [pət̪əɲɟəli]; fl. 150 BCE or 2nd c. BCE) is the compiler of the Yoga Sūtras, an important collection of aphorisms on Yoga practice. According to tradition, the same Patañjali was also the author of the Mahābhāṣya, a commentary on Kātyāyana’s vārttikas (short comments) on Pāṇini’s Aṣṭādhyāyī as well as an unspecified work of medicine (āyurveda). In recent decades the Yoga Sutra has become quite popular worldwide for the precepts regarding practice of Raja Yoga and its philosophical basis. “Yoga” in traditional Hinduism involves inner contemplation, a system of meditation practice and ethics.
Definition courtesy Wikipedia.