। ॥ ९२१ ॥
In plain words
When the mind's movements are completely forgotten — that is samādhi, and it goes by the name dhyāna as well. But once you actually take up that absorption, the obstacles arrive. And they arrive with force.
Close to the Sanskrit
The complete forgetting of the mind's modifications is samādhi, which carries the name dhyāna. But when samādhi is being practised, obstacles indeed come, and certainly they come forcibly.