Vulgar term for the anus, equivalent to 'asshole' or 'arsehole'. Used in crude or insulting contexts.
See also: ケツの穴
That guy is a real asshole.
My asshole hurts.
Most common vulgar spelling using ケツ for 'butt'.
Kanji spelling using 尻 (buttocks); less common but still encountered.
Compound of ケツ (slang for 'buttocks') and 穴 (hole). The reading けつあな is standard; しりあな is a search-only kana form.