। ॥ २१८ ॥
In plain words
One who knows sets the mind fully on the reality that is to be known, so as to sink into the meaning the Śruti declares. That settling is called samādhāna.
Close to the Sanskrit
For the sake of plunging into the meaning stated by the Śruti, the complete fixing of the mind by the knower upon the reality to be known — that is called samādhāna.