Final answer:
The phrase 'sepulchre' in the passage from Hamlet means 'grave'.
Step-by-step explanation:
The phrase 'sepulchre' in the passage from Hamlet refers to the 'grave'. This is evident from the phrases 'sepulchre, Wherein we saw thee quietly inurn’d', which implies a burial place, and 'Hath op’d his ponderous and marble jaws', which describes the opening of the grave.