This is the 328th most frequent French word.
gros
Big, large, fat.
Here, 'gros' is used as an adjective meaning 'big' or 'large', commonly applied to describe size in a positive or neutral manner.
Cet éléphant est très gros.
This elephant is very big.
In this sentence, 'grosse' conveys intensity or significance, describing an important or critical situation.
J'ai une grosse urgence au travail.
I have a pressing emergency at work.
The word 'grosse' here intensifies the noun it modifies, suggesting the mistake is serious or notable in impact.