folie

/fɔ.li/
1.
nounfeminine

madness

insanity

Son comportement relève de la folie.

His behaviour amounts to madness.

2.
nounfeminine

foolishness

a stupid or reckless act

C'est de la pure folie de sortir par ce temps.

It's pure madness to go out in this weather.

3.
nounfeminine

something amazing or wild (colloquial)

an extravagance or splurge

a craze, widespread mania

Leur soirée hier, c'était une folie !

Their party yesterday was wild!