Without scales, like a snake or a fish without the small, thin plates on their skin.
Being scaleless is just a natural way some animals are, like snakes and fish.
Examples:
The snake is scaleless and smooth.
The fish in the lake is scaleless.
She saw a scaleless lizard in the desert.
The scaleless fish looks like a big worm.
The scaleless snake feels very strange to touch.
The scaleless lizard is very interesting to look at.