Pouring with rain; wet; showery
"The sudden squall turned the dry path into a slippery mess, proving how quickly it can turn from sunny to rainy."
In plain English: Rainy means it is raining outside with wet clouds and falling water drops.
"The rainy afternoon kept us inside playing board games."
Rainy comes from the Old English word reġniġ, which is formed by combining "rain" with the suffix "-y." The term has traveled directly into modern usage without a significant shift in its original meaning.