cobble
n. C / Un. a small, round stone that has been worn smooth by water or wind. You often see them on the bottom of rivers or on the beach.
n. a small, rounded stone or pebble, typically smoothed by the action of water or wind. Often used in geological contexts to describe sedimentary particles.
The riverbed was covered in smooth cobble.
Geologists examined the cobble to determine how long the river had been flowing through the valley.
The sedimentary layer was composed primarily of angular cobble and sand, suggesting a high-energy environment where the water moved quickly enough to transport larger particles.
From Middle English cobill, kobill (used in various combinations with ston, stan (“stone”), note, nutt (“nut”), etc.), probably a diminutive of Middle English cob, cobb, ultimately from Proto-Germanic *kubb- (“lump; round object”). Equivalent to cob + -le.
See coble.