What does marathrum mean in Latin?

marathrum, a noun, means “fennel”.

What is the genitive of marathrum?

The genitive singular is marathrī. marathrum is neuter, second declension.

In classical Latin, [ˈma.ra.tʰrũː]; in ecclesiastical (church) Latin, [ˈmaː.ra.trum].

noun · neutersecond declension

marathrum n (genitive marathrī)

Classical[ˈma.ra.tʰrũː]Ecclesiastical[ˈmaː.ra.trum]

From Ancient Greek μάραθρον (márathron), μάραθον (márathon).

Elsewhere

Dalmatian