All 6 Uses of

renaissance
in
The Magic Mountain

The Renaissance, the Enlightenment, and the teachings of nineteenth-century science and economics have omitted nothing, absolutely nothing, that seemed even vaguely useful for furthering such degradation, beginning with modern astronomy—which turned the focal point of the universe, that sublime arena where God and Satan struggled to possess the creature whom they both ardently coveted, into an unimportant little planet, and, for now at least, has put an end to man's grand position in the cosmos, upon which astrology was likewise based.
Chpt 6.3

Renaissance = a period of European history known for a revival of intellectual and artistic achievement (14th through mid-17th centuries)

Or, conversely, your Renaissance astronomers discovered the truth, and the cosmos is infinite, which means there is no world that transcends the senses, no dualism; the world beyond is absorbed into this world, the polarity of God and nature is annulled, and since the human personality is no longer the battlefield of two hostile principles, but rather harmonious and unified, all human conflict stems from the clash between the interests of the individual and of society as a whole, and so the purpose of the state become the law of morality, just as in good old heathen days.
Chpt 6.3

The achievements that the Renaissance and the Enlightenment wrested from the past—and may I emphasize, my dear sir, the struggles contained in that verb—were individual human personality, human rights, and human freedom.
Chpt 6.3

I am more or less aware that the Renaissance gave birth to what is known as liberalism, individualism, humanistic citizenship, and all that.
Chpt 6.3 *

Hans Castorp picked up a newspaper, and moving toward the open door that led to the music room, he sat down, his back to the portieres, on the chair that happened to be there—a plush-covered Renaissance chair, with a high, straight back and no arms, for those who wish to visualize it.
Chpt 7.3

Definitions:

(1) (renaissance as in: a renaissance)
a revival or renewed interest in something
(2) (Renaissance as in: The Renaissance)
the period of European history known for a revival of intellectual and artistic achievement (14th through mid-17th centuries)

Named as an indication of a rebirth of certain classical ideas that had long been lost to Europe. It has been argued that the movement was strongly influenced by the rediscovery of ancient texts that had been forgotten by Western civilization, but were preserved in some monastic libraries and in the Islamic world, and the translations of Greek and Arabic texts into Latin.

Some historians have suggested that the term Renaissance is loaded and are suggesting the term Early Modern to replace it -- as Middle Ages has largely replaced Dark Ages for the period that preceded the Renaissance.
(3) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

Less commonly, Renaissance can be used as part of a proper noun referring to a period of revival or renewed interest other than the European Renaissance.