What does Telamōnius mean in Latin?

Telamōnius, a proper noun, means “son of Telamon, Ajax the Great”.

What is the genitive of Telamōnius?

The genitive singular is Telamōniī. Telamōnius is masculine, second declension.

In classical Latin, [tɛ.ɫaˈmoː.ni.ʊs]; in ecclesiastical (church) Latin, [te.laˈmɔː.ni.us].

proper noun · masculinesecond declension

Telamōnius m sg (genitive Telamōniī or Telamōnī)

Classical[tɛ.ɫaˈmoː.ni.ʊs]Ecclesiastical[te.laˈmɔː.ni.us]

son of Telamon, Ajax the Great
...quo si Telamonius isset, / orba suis essent etiam nunc lintea ventis.If Telamon’s son had gone, our sails would still be waiting for the winds.8 CE, Ovidius, Metamorphoses 13.194
utque sedet uultu fassus Telamonius iram, inque oculis facinus barbara mater habet,Not only does Ajax sit there, his look betraying wrath, and savage Medea, a mother with sin in her face, but Venus, damp, too, wringing wet hair in her fingers,8 CE – 12 CE, Ovidius, Tristia 2.525

From Τελαμώνιος (Telamṓnios).