désemparer

Almost always encountered in the fixed expression sans désemparer — "without stopping, relentlessly, without a break" (travailler sans désemparer). As a standalone verb outside this expression, désemparer is dated and literary for "to give up, to be at a loss."

• Elle a travaillé toute la nuit sans désemparer. — She worked all night without stopping.
• Les secouristes ont continué sans désemparer malgré la fatigue. — The rescue workers carried on without letting up despite their exhaustion.
• Il plaida sa cause sans désemparer pendant des heures. — He pleaded his case relentlessly for hours.

Outside the set phrase sans désemparer, this verb is rarely used on its own in modern French — don't expect to conjugate it as freely in casual speech as an ordinary verb.

• expression sans désemparer — A standard literary/formal fixed expression meaning "without stopping, relentlessly" — confirmed by Expressio.fr and Le Robert as a genuine, still-used locution describing sustained, uninterrupted effort.