This is the 3129th most frequent French word.
poussière
Dust.
Here, 'poussière' is used in its literal meaning, referring to the fine particles that collect on surfaces.
La vieille étagère était couverte de poussière.
The old shelf was covered in dust.
In this sentence, 'poussière' is used metaphorically to indicate a very small amount of something (hope).
Il n'a laissé qu'une poussière d'espoir dans son cœur.
He only left a speck of hope in his heart.
In this context, 'poussière' describes the atmospheric particles stirred up by the storm.