whonbatto means "Wombat" in English.
It's a katakanization, a loan-word.

whonbatto is normally written with katakana, as ウォンバット.
whonbatto written with hiragana is うぉんばっと.
whonbatto does not have kanji.
Romaji who n ba tto

Orthography Notes

  • ウォ is a compound kana representing a single syllable with multiple characters.
  • ット contains a small tsu which makes the consonant of the syllable longer.

Further Reading

Wikipedia: ウォンバット (Wombat)