This is the 2253rd most frequent French word.
grosses
"Grosses" means "big" or "large" (feminine plural form).
In this sentence, 'grosses' is the plural feminine form of the adjective 'gros', used metaphorically to describe the twins before birth.
Elle attend des jumelles précieuses et grosses.
She is expecting precious and hefty twins.
'Grosses' here is the plural feminine form of the adjective 'gros', referring to the size of the balloons.
Les ballons dans le magasin étaient tous très grosses.
The balloons in the store were all very large.
Here, 'grosses' is used as the plural feminine form of the adjective 'gros', describing large apples.