What does būnion mean in Latin?

būnion, a noun, means “a type of turnip, perhaps earthnut, Bunium ferulaceum”.

What is the genitive of būnion?

The genitive singular is būniī. būnion is neuter, second declension.

In classical Latin, [ˈbuː.ni.ɔn]; in ecclesiastical (church) Latin, [ˈbuː.ni.on].

noun · neutersecond declension

būnion n (genitive būniī)

Classical[ˈbuː.ni.ɔn]Ecclesiastical[ˈbuː.ni.on]

a type of turnip, perhaps earthnut, Bunium ferulaceum
Nāpōrum duās differentiās et in medicīnā Graecī servant. Angulōsīs foliōrum caulibus, flōre anētī, quod būnion vocant, pūrgātiōnibus fēminārum et vēsīcae et ūrīnae ūtile dēcoctum, pōtum ex aquā mulsā vel sūcī drachmā; sēmen dysintericīs tostum trītumque in aquae calidae cyathīs quattuor. sed ūrīnam inhibet, sī nōn līnī sēmen ūna bibātur.The Greeks also preserve two distinct types of turnip in medicine. With angular leafstalks and a flower like that of dill, the one they call the “bunion” is useful boiled, drunk in mead or in a drachma of juice for women's purgings and for the bladder and for the urine; the seed, toasted and ground, in four ladlesful of warm water, (is useful) for people with dysentery. It prevents urination, however, if one (drachma) of linseed is not drunk.77 CE – 79 CE, Plinius Maior, Naturalis Historia 20.11

From the Ancient Greek βούνῐον (boúnĭon).