Chakra is a concept originating from Hindu texts and used in Hindu practices. Its name derives from the Sanskrit word for “wheel” or “turning” (cakraṃ चक्रं [ˈtʃəkrə̃], pronounced [ˈtʃəkrə] in Hindi; Pali: cakka चक्क, Thai: จักระ, Tamil: சக்கரம், Chinese: 轮, Tibetan: འཁོར་ལོ་; khorlo).
Chakra is a concept referring to wheel-like vortices which, according to traditional Indian medicine, are believed to exist in the surface of the etheric double of man. The Chakras are said to be “force centers” or whorls of energy permeating, from a point on the physical body, the layers of the subtle bodies in an ever-increasing fan-shaped formation. Rotating vortices of subtle matter, they are considered the focal points for the reception and transmission of energies. Different systems posit a varying number of chakras; the most well known system in the West is that of seven chakras.
It is typical for chakras to be depicted as either flower-like or wheel-like. In the former, “petals” are shown around the perimeter of a circle. In the latter, spokes divide the circle into segments that make the chakra resemble a wheel (or “chakra”). Each chakra possesses a specific number of segments or petals.
Texts describing the chakras go back as far as the later Upanishads, for example the Yoga Kundalini Upanishad.
Definition courtesy Wikipedia.