What does the word crust mean?

Usage examples for crust

  1. These men are all upper crust here. – The Attache or, Sam Slick in England, Complete by Thomas Chandler Haliburton
  2. Rollo and Lucy were going to have an expedition upon the crust. – Rollo's Philosophy. [Air] by Jacob Abbott
  3. The upper crust would sometimes support a man's weight for a short time, and then suddenly let him down two or three feet, so that we could never make sure of our footing for two steps together. – Three Voyages for the Discovery of a Northwest Passage from the Atlantic to the Pacific, and Narrative of an Attempt to Reach the North Pole, Volume 2 (of 2) by Sir William Edward Parry