Very bad or serious, like a severe storm or a severe injury.
Severe things are not good and can be very dangerous or painful.
Examples:
The storm was severe and caused a lot of damage.
She had a severe headache and had to lie down.
The doctor said it was a severe illness.
I got a severe scolding for breaking the window.
The punishment was severe, I had to sit in the corner for a whole hour.
The severe pain made him cry.