समाधिरात्मनो नाम नान्यच्चित्तस्य विभ्रमः ।तत्रैव ब्रह्मणि सदा चित्तविश्रान्तिरिष्यते ॥ ३१ ॥
In plain words
Samādhi means absorption in the Self — nothing else earns the name; anything else is the mind wandering. There, in Brahman, and always: that resting of the mind is what is meant.
Close to the Sanskrit
Samādhi is, properly so called, of the Self; nothing else — [that] is the mind's wandering. There alone, in Brahman, the mind's resting is always held [to be samādhi].