This is the 5856th most frequent French word.
croissant
A flaky, crescent-shaped pastry.
In this sentence, 'croissant' refers to the crescent-shaped pastry often eaten for breakfast.
Je mange un croissant au petit-déjeuner.
I eat a croissant for breakfast.
Here, 'croissant' relates to the crescent shape of the moon phase.
La lune était en croissant hier soir.
The moon was a crescent last night.
In this context, 'croissant' is used as an adjective meaning 'increasing' or 'growing.'