When something is shapeless, it doesn't have a clear or definite shape.
Shapeless things might look messy or undefined.
Examples:
The blob of clay is shapeless.
Her dress is shapeless and doesn't fit well.
The shapeless cloud covered the sky.
The shapeless cake looked like a big mess.
After the dog sat on it, the pillow became shapeless.
The shapeless monster in the movie was very scary.