What does "rainy day" mean?

A difficult period of need, in reference to a time when money will be needed.

Rainy day

Common synonyms include: bad times, bust, cat-and-dog weather, depression, dirty weather, economic stagnation.

noun

noun ·Rare ·Advanced level

Noun

1
A difficult period of need, in reference to a time when money will be needed. idiomatic
"I've kept some money in the bank for a rainy day."
2
a (future) time of financial need wordnet
3
Used other than figuratively or idiomatically: see rainy, day.
"Rainy days and Mondays always get me down."

"I've kept some money in the bank for a rainy day."