To roughen means to make something less smooth by creating an uneven, coarse, or bumpy surface. When you roughen wood with sandpaper before painting it, you're creating tiny scratches that help the paint stick better. A chef might roughen the outside of a potato with a fork before baking it so the skin gets extra crispy.

The word works as a verb in different contexts. Cold winter winds can roughen your skin, making it dry and flaky instead of soft. A carpenter might deliberately roughen a slippery wooden step to make it safer to walk on. Athletes sometimes roughen the grip on their tennis rackets or baseball bats so they won't slip during play.

You might also hear the word used about voices: when someone has a cold or has been shouting, their voice can roughen, becoming hoarse and scratchy instead of clear and smooth.

The opposite of roughen is smooth or polish. While you roughen surfaces when you need better grip or texture, you smooth them when you want them sleek and glossy.