A person who meddles or intrudes in other people's affairs; one who butts in uninvited (informal/slang).
From butt in (to intrude) + -ski (a Yiddish-influenced suffix used for creating English slang terms). The -ski ending is found in beatnik-era slang.
Buttinski is brilliantly artificial—created by smooshing 'butt in' with a fake Slavic suffix to create a comedic effect, showing how mid-20th-century American slang played with language as performance.
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