magnum opus

mag´num o´pus Pronunciation: măg´nŭm ō´pŭs

n.	1.	A great work of art or literature.
	2.	The greatest work or achievement of a particular artist, writer, or other individual. Inspired by this milieu, [Max Stirner] wrote his magnum opus The Ego and Its Own, which was published in November 1844. - Svein Nyberg (The Small Max Stirner Web Page, 1988 [http://www.math.uio.no/~solan/stirner/stirner.html]

Noun

magnum opus - a great work of art or literature