The Yoga Sutras by Patanjali open with the quintessential definition of yoga, which is also a quintessential definition of meditation:
1.2 Yoga is the stilling of the fluctuations of the mind.
1.3 Then the True Self is revealed.
With the Western tendency to overemphasis yoga postures, we have seen a strange division between yoga (erroneously equated with yoga postures) and meditation, as though the two were seperate. Yet yoga embraces the whole mandala of practice and of life itself. Yoga embraces the spinning wheel of experience though the body, heart, mind and spirit. At the very hub of the spinning wheel of life, of practice, of yoga is meditation. Yoga is meditation is yoga.