Meaning of anchor ball

an'chor ball"

Pronunciation: [key]
— Naut. Naut.
  1. a day shape consisting of a black ball not less than 2 ft. (0.6 m) in diameter, displayed in the fore rigging of a vessel at anchor.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.