From Longman Dictionary of Contemporary Englishpebblepeb‧ble /ˈpebəl/ ●○○ noun [countable] 
DNa small smooth stone found especially on a beach or on the bottom of a river The beach was covered with smooth white pebbles. —pebbly adjective a pebbly beach
DNa small smooth stone found especially on a beach or on the bottom of a river The beach was covered with smooth white pebbles. —pebbly adjective a pebbly beachExamples from the Corpus
pebble• He says they have to put a pebble in their hand down south so they know left face from right face.• There was a brighter rattle, as of something small and hard, like pebbles.• Like pebbles underwater, flickering with the light.• A shower of pebbles fell short of her shin.• Mist them frequently or place the container on a tray of pebbles and water.• Spray some pebbles silver and use an indelible pen to number them I to 24.• However, convincing myself the pebbles I was climbing on wouldn't pull out did take a little time.• He ripped up grass; tore apart moss; picked up pebbles, sticks, and twigs.Origin pebble Old English papolstan, from papol (perhaps from the sound of small stones hitting against each other) + stan “stone” 