What does Latīnum mean in Latin?

Latīnum, a proper noun, means “Latin (language of the ancient Romans)”.

What is the genitive of Latīnum?

The genitive singular is Latīnī. Latīnum is neuter, second declension.

In classical Latin, [ɫaˈtiː.nũː]; in ecclesiastical (church) Latin, [laˈtiː.num].

proper noun · neutersecond declension

Latīnum n sg (genitive Latīnī)

Classical[ɫaˈtiː.nũː]Ecclesiastical[laˈtiː.num]

Latin (language of the ancient Romans)
[…]licet enim, ut sæpe facimus, in Latīnum illa convertere:[…] it is therefore proper, as we often do, to translate those things into Latin:106 BCE – 43 BCE, Cicero, Tusculanae Disputationes 3.29
Hās rēs commodissimē Xenophōn Socrāticus persecūtus est in eō librō, quī 'Œconomicus' īnscrībitur, quem nōs, istā ferē̆ ætāte cum essēmus, quā es tū nunc, ē Græcō in Latīnum convertimus.Xenophon agreeably discussed this topic in his book entitled Oeconomicus, which I translated when I was almost your age, from Greek into Latin.44 BCE, Cicero, De officiis 2.87