This is the 119th most frequent French word.
grande
"Grande" means "big" or "large" in English.
Here, 'grande' is an adjective describing the noun 'maison' (house) and indicates size.
C'est une grande maison.
It's a big house.
Here, 'grande' connotes something remarkable or noteworthy, used figuratively.
C'était une grande journée pour nous tous.
It was a great day for all of us.
In this case, 'grande' is used metaphorically to mean 'important' or 'significant' rather than literally large.