Translation

The Japanese word for "Donkey" is roba ロバ.

Romaji ro ba
Hiraganaろば
Katakanaロバ
Kanji 驢 馬
Meaning Donkey Horse
School Level ✕ 小2

Loan-word

The word "Donkey" katakanized would be donkī ドンキー.
Romaji do n kii
Katakanaドンキー
Hiraganaどんきー

Synonyms

Ass.

Further Reading

Wikipedia: Donkey (ロバ)
ashika 海驢.