What does “hors sujet” mean in French?

“Hors sujet” literally means “outside the subject” — off-topic, beside the point, not what was asked. It’s the nightmare of French exams: write a brilliant essay that misses the prompt and you’ve “fait du hors sujet,” earning almost nothing however well-written. Beyond school, être hors sujet calls out any remark that strays from the matter at hand. The opposite is rester dans le sujet, staying on point.

Here a student sums up the wait for results as a gamble: “soit j’ai bien compris mon sujet… soit j’ai fait du hors sujet” — either I understood the commentary prompt, or I went off-topic. Note the spelling: the noun is often hyphenated (un hors-sujet), while the phrase être / partir hors sujet usually isn’t. A close cousin is être à côté de la plaque — wide of the mark.