What is "mangolds"

Usage examples of "mangolds".

In the afternoon the police had come, and the laborers had rushed with Derek and Sheila, who had joined them, into a barn at Marrow Farm, barred it, and thrown mangolds at the police, when they tried to force an entrance.

Derek, who had stayed to the last, covering their escape with mangolds, had jumped down twenty feet when he saw them taking Sheila, and, pitching forward, hit his head against a grindstone.