also: くそまじめ · クソマジメ
overly serious; serious to a fault; humorless
Describes a person or attitude that is excessively earnest, rigid, or lacking in humor, often with a negative or mocking tone. The prefix クソ adds a vulgar, emphatic nuance similar to 'damn' or 'stupidly'.
He's so overly serious that jokes don't get through to him.
He said something weird with a dead-serious face, so I burst out laughing.
Neutral term for 'serious' or 'diligent'. クソ真面目 adds a vulgar, emphatic prefix that makes it derogatory or mocking.
Means 'overserious' or 'strait-laced' without the vulgarity; クソ真面目 is more colloquial and harsher.
Common mixed kanji-katakana spelling; the prefix クソ is often written in katakana for emphasis.
Full kanji spelling; the kanji 糞 is uncommon and may be considered vulgar or overly literal.
Hiragana prefix variant; less emphatic than the katakana form.
All-katakana spelling; used for strong emphasis or in informal writing.
Compound of the vulgar intensifier クソ (kuso, 'damn') and 真面目 (majime, 'serious'). The prefix クソ is used here to express an extreme or excessive degree, often with a derogatory nuance.