What term describes the act of placing remains in a crypt in a mausoleum?

The term that describes the act of placing remains in a crypt in a mausoleum is "entombment." This practice specifically refers to the interment of a body within a tomb or vault, distinguishing it from other methods of disposition like burial in the ground or cremation. When individuals are placed in a mausoleum, they generally occupy sealed compartments known as crypts, which are designed for the respectful and permanent storage of remains, often in a memorial setting.

Interment typically refers to the broader act of burial which can occur in a graveyard, while cremation involves the process of reducing a body to ashes through intense heat, and inurnment refers to placing the ashes in an urn. Therefore, entombment is the most accurate term for the specific action of placing remains within a mausoleum.