How to say "ass" in Japanese

Choosing the right word

けつ
nounThe blunt colloquial term for a person's buttocks or backside, matching 'ass' and 'arse'; it belongs to rough casual speech and would sound out of place in polite contexts.
時々ときどき、自分じぶんのけつを思おもいきり蹴けりあげてやりたくなる。↗
Sometimes I feel like kicking my own rump.
ろば
nounThis word covers the animal sense of 'ass': it means 'donkey'. If you mean a person's backside, this is not the word you want.
あれは馬うまではなくロバだ。↗
That is not a horse, but a donkey.
太ももふとももCommon
nounA common word that literally means 'thigh'; its colloquial 'ass' and 'butt' glosses are loose extensions from that region, so it is only marginally a word for the backside.
どんじり
nounA derogatory word for someone's rear end, matching 'ass' and 'butt'; its insulting tone suits mockery or angry complaints, not neutral description.

For the body part, 「けつ」 is the blunt colloquial term and 「どんじり」 the derogatory one, while 「太もも」 is really the thigh; for the animal, use 「ろば」.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

Japanese equivalents

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