What does the word cornerstone mean?

Usage examples for cornerstone

  1. He had no expectation, however, of ever living such a life, for pride, the cornerstone of his character, had given way, and he was too greatly discouraged at the time to purpose reform even in the future. – A Knight Of The Nineteenth Century by E. P. Roe
  2. Integrity of word and deed ought to be the very cornerstone of all business transactions. – Self Help by Samuel Smiles
  3. Now he's the cornerstone of Ace Books. – Uller Uprising by Henry Beam Piper, John D. Clark and John F. Carr