What does acherontēus mean in Latin?

acherontēus, a adjective, means “related to Acheron; underworldly”.

How do you pronounce acherontēus?

In classical Latin, [a.kʰɛ.rɔnˈteː.ʊs]; in ecclesiastical (church) Latin, [a.ke.ronˈtɛː.us].

adjectivefirst/second-declension adjective

acherontēus (feminine acherontēa, neuter acherontēum)

Classical[a.kʰɛ.rɔnˈteː.ʊs]Ecclesiastical[a.ke.ronˈtɛː.us]

singular
form	masculine	feminine	neuter
nominative	acherontēus	acherontēa	acherontēum
genitive	acherontēī	acherontēae	acherontēī
dative	acherontēō	acherontēae	acherontēō
accusative	acherontēum	acherontēam	acherontēum
ablative	acherontēō	acherontēā	acherontēō
vocative	acherontēe	acherontēa	acherontēum

plural
form	masculine	feminine	neuter
nominative	acherontēī	acherontēae	acherontēa
genitive	acherontēōrum	acherontēārum	acherontēōrum
dative	acherontēīs	acherontēīs	acherontēīs
accusative	acherontēōs	acherontēās	acherontēa
ablative	acherontēīs	acherontēīs	acherontēīs
vocative	acherontēī	acherontēae	acherontēa

Borrowed from Ancient Greek Ἀχερόντειος (Akherónteios).