noun | verb
rockrock1 /rɑk/ noun 
► rock a piece of a hard natural substance on or in the ground. A rock can be big or small: Finn sat on a rock at the bottom of the trail. The waves washed over the rocks at the bottom of the cliff. She picked up a rock and threw it into the water. ➔ Rock also means the hard substance that forms part of the Earth's surface: You can see the different layers of rock in the Grand Canyon.
► stone a small rock: Protesters threw stones at the police. ➔ Stone also means rock that has been shaped to use for building things: The houses are made of stone.
► boulder a large rock: A huge boulder rolled down the mountain.
► pebble a small smooth stone: I got a pebble in my shoe as I was walking down the trail.
► fossil a rock that shows part of an animal or plant that lived thousands or millions of years ago: Scientists found dinosaur fossils that were over 130 million years old.
noun | verb
rockrock2 /rɑk/ verb ► rock to move from side to side or backward and forward in a gentle way: The boat rocked with the movement of the waves. He sat in the chair, rocking backward and forward. ➔ You can also use rock when you make something move from side to side or backward and forward: She was rocking the baby in her arms.
► sway to move slowly from side to side. People, buildings, and trees sway: Office buildings started to sway as the earthquake hit. Her body swayed with the music.
► wobble to move from side to side in an unsteady way: The ladder wobbled and I was worried that it was going to fall over.
► swing to move backward and forward or from side to side with long movements. You use swing when talking about the movement of things that hang from something or are attached to something at one side: Jack tried to grab the rope which was swinging backward and forward. The door kept swinging open and shut in the wind. ➔ You can also use swing when you make something move backward and forward or from side to side: The girl was sitting on the desk, swinging her legs.