construction stone (approx. 10-15 cm)
Technical term in civil engineering and construction for stones of a specific size range, roughly chestnut-sized.
chestnut-sized pebble
Rare general term for a pebble about the size of a chestnut; the construction sense is far more common.
In foundation work, they spread chestnut-sized stones before pouring concrete.
I picked up a stone about the size of a chestnut by the river.
Compound of 栗 (chestnut) and 石 (stone), referring to the chestnut-like size of the stones.