Very casual, often vulgar word for the buttocks. Used among close friends or in rough speech.
Only when written 穴
Technical term in acupuncture, using the kanji 穴. Not used in everyday conversation.
This pressure point is one of the acupuncture points.
Only when written 穴
Counter for holes or notches, using the kanji 穴. Rare and specialized.
I gave my subordinate a kick in the pants to get the work moving.
I fell and hit my ass.
That guy has a huge butt.
Please line up at the end of the queue.
The rear of the car got hit.
I made one hole in the belt.
I bumped into the back of the car.
If something goes wrong, I'll take responsibility.
The deadline is approaching, and I'm really under the gun.
臀部 is a formal, medical term for the buttocks, whereas ケツ is crude slang used in casual or rough speech.
お尻 is the standard, polite word for buttocks, while ケツ is a rough, casual (often vulgar) term for the same body part.
穴 read あな means a hole or gap in everyday use, while the same kanji read ケツ is slang for buttocks or a technical acupuncture-point/counter term.
grave; burial pit
cave dwelling; troglodytism
acupuncture point
one hole; single hole · combined toilet bowl; toilet for both urination and defecation · effective moxibustion point; single acupoint for moxibustion · one-woman man; man devoted to one woman
the seven orifices of the head
two holes · toilet with separate chambers for urine and feces · riding double (on a bicycle, motorcycle, etc.)
being buried in the same grave
dark hole; dark pit · idiot; fool · road taken by a Chinese ajari monk fleeing Emperor Xuanzong's wrath
posthole
Katakana spelling is common in casual writing; the word is usually written in kana.
Hiragana spelling, also common.
Kanji spelling used for the acupuncture point and counter senses; rarely used for the body part.
Kanji spelling for the body part, but very rare; usually written in kana.
The slang form ケツ is based on the Sino-Japanese reading けつ of 穴 “hole,” used especially for the anus and subsequently extended to the buttocks, rear, and end.
pressure points; acupoints · vulnerable body cavities; vital points
pothole; giant's kettle
cluster of Kofun-period graves
crevice; aperture