Meaning of whistling buoy

whis'tling bu'oy

Pronunciation: [key]
— Naut. Naut.
  1. a buoy having a whistle operated by air trapped and compressed in an open-bottomed chamber by the rising and falling water level caused by natural wave action.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.