This is the 411th most frequent French word.
grandes
The French word "grandes" means "big" or "tall" in English (feminine plural form).
In this sentence, "grandes" is used as an adjective to describe the noun "montagnes" (mountains), indicating their large size.
Les grandes montagnes dominent l'horizon.
The large mountains dominate the horizon.
Here, "grandes" describes the noun "idées" (ideas), conveying the grandeur or ambitious nature of the ideas.
Elles ont de grandes idées pour le projet.
They have grand ideas for the project.
In this usage, "grandes" characterizes "personnes" (persons) to refer to adults or elder individuals, indicating their maturity or age.