To severe something means to cut it off or break it apart.
Severing something can be a big and serious thing, like cutting a rope or breaking a bone.
Examples:
She will severe the rope with scissors.
The strong wind will severe the tree branch.
He accidentally severed the power cord with a shovel.
I hope I don't severe my sandwich in half!
The superhero can severe metal with his laser eyes.
The magician will severe the rope and make it whole again.