Definition of "Billy"

Billy

/ˈbɪli/

proper noun
1. A diminutive of the male given name William.
  Quotations
  “By the way,” Jessamy went on, “what’s your other name? You never told me.” “Stubbs,” said Billy, “William Stubbs!”.
  1967, Barbara Sleigh, Jessamy, Sevenoaks, Kent: Bloomsbury, published 1993, page 98
2. (US, nickname) The B-25 twin-engine bomber aircraft used during World War Two, commonly called the "B-25 Mitchell" in honor of U.S. Army General William "Billy" Mitchell.