LATIN DICTIONARYLexicon Latīnum
noun · neutersecond declension

altum1

altum n (genitive altī)
Classical[ˈaɫ.tũː]Ecclesiastical[ˈal.tum]

Meaning

  1. neuterthe deep, the sea
  2. neuterthe height (of heaven)
    Haec ait, et Māiā genitum dēmittit ab altō, ut terrae, utque novae pateant Karthāginis arcēs hospitiō Teucrīs, nē fātī nescia Dīdō fīnibus arcēret: volat ille per āera magnum29 BCE – 19 BCE, Vergilius, Aeneis 1.297.301

Latīnē defined in Latin in our graded readers

Declension

declension
formsingularplural
nominativealtumalta
genitivealtīaltōrum
dativealtōaltīs
accusativealtumalta
ablativealtōaltīs
vocativealtumalta

altum, i, n., v. altus, P. a. from alo.

Origins

Forms of altus. The adverb is an adverbial accusative.

adverb
altum2
altum (not comparable)
Classical[ˈaɫ.tũː]Ecclesiastical[ˈal.tum]

Meaning

  1. not comparableraredeeply

Charlton Lewis's shorter dictionary for students: the same scholarship in plain, modern definitions.

altum adv.
altus, deeply: dormire, Iu.

Origins

Forms of altus. The adverb is an adverbial accusative.

Quick answers

What does altum mean in Latin?
altum, a noun, means “the deep, the sea; the height (of heaven)”.
What is the genitive of altum?
The genitive singular is altī. altum is neuter, second declension.
How do you pronounce altum?
In classical Latin, [ˈaɫ.tũː]; in ecclesiastical (church) Latin, [ˈal.tum].