What does chitinum mean in Latin?

chitinum, a noun, means “chitin”.

What is the genitive of chitinum?

The genitive singular is chitinī. chitinum is neuter, second declension.

In classical Latin, [ˈkʰɪ.tɪ.nũː]; in ecclesiastical (church) Latin, [ˈkiː.ti.num].

noun · neutersecond declension

chitinum n (genitive chitinī)

Classical[ˈkʰɪ.tɪ.nũː]Ecclesiastical[ˈkiː.ti.num]

neuterchitin
Penis longitudinis 3 mm, glans mobiles, color chitini penis flavescens, ceterum vide figuram.Penis 3 mm long, glans mobile, color of the chitin of the penis yellowish, otherwise see figure.1946, Vladimir Šilhavý, “Nový rod a druh sekáčů, Odontosoma centetes, nov. gen., nov. spec. (Opiliones, subfamilia Phalangiinae)”, in Sborník Přírodovëdeckého klubu v Třebíči za rok 1939-1944. (overall work in Czech and Latin), Třebíč, page 57 of 55-57:

Ancient Greek χῐτών (khĭtṓn)bor. Latin chitōn Proto-Indo-European *-om Proto-Italic *-om Latin -um Latin chitinum From chitōn + -um.