This is the 1953rd most frequent French word.
seuil
Threshold.
In this sentence, 'seuil' is used in its literal meaning to refer to the base of a doorway.
Le seuil de la porte est propre.
The threshold of the door is clean.
'Seuil' is used metaphorically here to indicate the beginning or brink of a substantial event.
Le pays est au seuil d'une révolution.
The country is on the verge of a revolution.
In this context, 'seuil' denotes a limit or point where a change occurs regarding tolerance.