An Epic
Epic, Epic Saga, Masterpiece, Masterwork, Magnum Opus
noun
The big make! What is your big make? Bigger than anything else. It is your epic (as in an epic that you write). Also could be an epic, epic saga, and masterpiece.
たいさく
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
このえいがは、ヒッチコックの大作だ。
This movie is a Hitchcock epic.
今世き一ばんの大作ともいわれているえいがのタイトルは「フグの一生」です。
The title of the most epic film this century is said to be, "A Life of Fugu."
ベートーベンが作曲した曲は、どれも大作だった。
Every score that Beethoven wrote was a masterpiece.