Part of Speech: Noun

Definition: An artistic work, especially one on a large scale

Source: Merriam-Webster Dictionary

Found in ”Lady Lazarus” by Sylvia Plath, “I am your opus / I am your valuable, / The pure gold baby” Line 67-69

The definition of the opus helped me understand the lines. I believe she referring herself to an art work and how meaningful and worth she is and how art work also a valuable connections between them.