What does urnārium mean in Latin?

urnārium, a noun, means “A table on which water-vessels were set.; an urn-table.”.

What is the genitive of urnārium?

The genitive singular is urnāriī. urnārium is neuter, second declension.

noun · neutersecond declension

urnārium n (genitive urnāriī or urnārī)

urnārĭum, ii, n. urna, I.,

I. a table on which water-vessels were set, an urn-table, Varr. L. L. 5, § 126 Müll.; id. ap. Non. 544, 20.

From urna + -ārium.