What is the act of placing the remains in a mausoleum crypt called?

The act of placing remains in a mausoleum crypt is referred to as entombment. This term specifically designates the process of housing human remains in a structure designed for this purpose, such as a mausoleum or tomb.

Entombment differs from other terms related to the final disposition of remains. For instance, inurnment refers to placing cremated remains in an urn, and interment typically means burying remains in the ground. Inhumement is less commonly used and generally signifies the act of burying remains as well, but it is not specific to mausoleum crypts. Thus, when discussing the specific context of placing remains in a mausoleum, entombment is the most accurate and appropriate term to use.