What does dominiōnus mean in Latin?

dominiōnus, a noun, means “donjon (central tower of a castle)”.

What is the genitive of dominiōnus?

The genitive singular is dominiōnī. dominiōnus is masculine, second declension.

noun · masculinesecond declension

dominiōnus m (genitive dominiōnī)

declension
form	singular	plural
nominative	dominiōnus	dominiōnī domniōnēs, dungiōnēs
genitive	dominiōnī domniōnis, dungiōnis	dominiōnōrum domniōnum, dungiōnum
dative	dominiōnō domniōnī, dungiōnī	dominiōnīs domniōnibus, dungiōnibus
accusative	dominiōnum domniōnem, dungiōnem	dominiōnōs domniōnēs, dungiōnēs
ablative	dominiōnō domniōne, dungiōne	dominiōnīs domniōnibus, dungiōnibus
vocative	dominiōne	dominiōnī domniōnēs, dungiōnēs

From Old French donjon and Old Occitan domnhon. First attested in the 1040s in a document from Mouzon.