Definition of "waterhole"

waterhole

noun
plural waterholes
1. A depression in which water collects, especially one where wild animals come to drink.
  Quotations
  From habit the sheep would head for the river, but, though it was early spring, the winter had been droughty, and the river was only a string of dangerous water-holes.
  1907, Barbara Baynton, edited by Sally Krimmer and Alan Lawson, Human Toll (Portable Australian Authors: Barbara Baynton), St Lucia: University of Queensland Press, published 1980, page 268
2. (informal) A watering hole; a place where people meet to drink and talk.
3. (astronomy) A part of the electromagnetic spectrum, between the regions where hydrogen and hydroxyl radiate, that is relatively quiet in terms of radio astronomy.