자갈

pebble; A small stone that is round and smooth as it has worn away on the floor of a river or the sea.

강이나 바다의 바닥에서 물에 닳아 둥글고 매끄러워진 작은 돌.

piece of gravel; A common, small stone that does not have a regular shape.

일정한 모양이 없는 평범한 작은 돌.