There are three distinct senses in which the word samadhi is used: 1) proper concentration, which is a necessary preliminary to the meditative states proper; 2) a general characteristic of the formal levels of meditational development (four dhyānas, four formless realms), which are entered through one-pointedness of mind; and 3) enlightened meditational states.

When you teach people in the world to cultivate samadhi, they must first of all sever the mind of lust. Therefore, Ānanda, if cultivators of dhyāna-samadhi do not eliminate lust, they will be like someone who cooks sand in the hope of getting rice. After hundreds of thousands of aeons it will still just be hot sand. Why? It wasn’t rice to begin with; it was only sand.(SSVI 13-14)

For someone who has the power of samadhi:
Even when Mount Tai topples over, I’m not scared.
Why? Its toppling over is the same as if it hadn’t toppled over.

When a pretty girl appears before me, I’m not moved.
Face to face with her, it’s as if I wasn’t. (EDR I 12)

“What is the meaning of proper concentration and proper reception’ (i.e., samadhi)? Proper concentration is a state of absorption where the mind is brought into focus which is proper and true and right, not biased or deviant. Proper reception means all that ‘comes in’—what you receive at that point—is right and appropriate. But you have to do the cultivation yourself. You can’t rely on the Buddhas and Bodhisattvas and expect them to give it to you. If you do the work, then the results are naturally yours.” (EDR VII 60)

三昧 / 三摩地 / 定