From "sam" (together or integrated), "a" (towards), and "dha" (to get, to hold). Thus the result might be seen to be to acquire integration or wholeness, or truth (samapatti).
Samadhi is the main subject of the first part of the Yoga Sutras called Samadhi-pada. According to Vyasa, a major figure in Hinduism and one of the traditional authors of the Mahabharata, "yoga is samadhi".
"Samadhi" also means "absorption" or "transcendence" and it is what we experience in daily meditation. It expands over time, eventually becoming our natural state of being in daily activity. It is pure bliss consciousness, the inner silent witness. Samadhi in its various stages of unfoldment is the experience of our immortal universal Self. That is what we are.