Meditation (dhyana) is a spiritual practice that aims to regulate, sense withdrawl (pratyahara), concentration (dharana), and ultimately transcend the mind.
In the eight limbs of Yoga, outlined in Patanjali's Yoga Sutras it comes as the final step before samadhi, oneness.

Eight Limbs of Yoga

1. Yama (abstinence)
2. Niyama (observance)
3. Asana (posture)
4. Pranayama (breath control)
5. Pratyahara (withdrawl of the senses)
6. Dharana (concentration)
7. Dhyana (meditation)
8. Samadhi (super-consciousness)

Dhyana
Sutra III.2
tatra pratyaya-ekatanata dhyanam

tatra = there, therein
pratyaya = presented idea
eka = one
ekatanata = one continuous flow of uninterrupted attention
dhyanam = meditative absorption

The repeated continuation, or uninterrupted stream of that one point of focus is called absorption in meditation (dhyana).