columbarium (pl. columbaria).
1. Colombier or dovecote, a substantial building commonly on a circular plan, with niches (columbaria) in tiers around the walls of the structure for nesting doves or pigeons, and an aperture or apertures to allow the birds to fly in and out.

2. Building or subterranean excavated tomb lined with niches to receive the cineraria or urns holding Roman cremated remains, so called from its resemblance to a dovecote, or any C19 or C20 building designed to contain such remains, as at Père-Lachaise, Paris.

3. Putlog-hole, from its resemblance to a niche in a dovecote.

Bibliography

J. Curl (2003c);
Toynbee (1971)

columbarium dove-cot; underground sepulchre with niches. XVIII. — L., f. columba dove, pigeon; see -ARIUM.