Comets are thought of as dirty snowballs, porous agglomerations of ice and rock.

A comet is like a huge dirty snowball, a mixture of ice and rocks.

But Ganymede looks like a dirty snowball next to Jupiter, the largest planet in our solar system.

"It looks like a dirty snowball to me."

Chiron was an obscure ice dwarf, a dirty snowball two hundred miles across.

The flak returned, chasing him with its dirty snowballs, and he was overtaken by rage.

It was a dirty snowball three hundred miles across, slowly turning in the outer darkness.

It might accurately be described as a dirty snowball hurled through space by the hand of God.

Then the whole dirty snowball was growing smaller.

They are often popularly described as "dirty snowballs."