Slang abbreviation of 刑務所 (けいむしょ). Used in casual, often rough or criminal contexts, similar to English 'slammer' or 'pen'.
See also: 刑務所
That guy just got out of the slammer.
I got thrown in the pen.
office
prison; jail; penitentiary
temple office
shrine office; Shinto shrine office
this office
Katakana spelling is common for this slang abbreviation; usually written in kana.
Kanji spelling is rare; the word is almost always written in kana. The kanji form is the same as the second part of 刑務所 (prison).
Slang abbreviation of 刑務所 (けいむしょ), dropping the first character and using the on'yomi reading of the remaining two.