This is the 11868th most frequent French word.
sueur
Sweat.
Here, 'sueur' refers to the physical manifestation of perspiration due to physical effort.
La sueur coule sur son front pendant qu'il court.
Sweat drips from his forehead as he runs.
In this usage, it represents committed effort or labor, often metaphorical.
Il a travaillé dur toute la journée, littéralement à la sueur de son front.
He worked hard all day, literally by the sweat of his brow.
Here, 'sueur' is used to describe a physical reaction associated with fear or anxiety.