Definition of "bowlder"

Between was the wild valley where cattle grazed among the trees and the massive bowlders.

1900, Gertrude Franklin Horn Atherton, The Doomswoman‎

His back humped; like a bowlder hurled down a mountain slope he made his rush, and nothing could swerve him.

1913, B. M. Bower, The Gringos‎

The trees on the summit bent in the wind; spray leaped about the bowlders where the white foam rolled.

1920, Harold Bindloss, Lister's Great Adventure‎

The first step in the construction was to outline the periphery of the base with bowlders of uniform size and weighing, perhaps, fifty pounds each.

1924, Edgar Rice Burroughs, chapter 6, in Tarzan and the Ant Men‎, 1st edition