D defs.my
Entry 1 sense Webster, 1913

Quadrillion

· Quad·ril·lion · IPA /kwɑˈdɹɪl.i.ən/
01 n. According to the French notation, which is followed also upon the Continent and in the United States, a unit with fifteen ciphers annexed; …
  1. 1.
    According to the French notation, which is followed also upon the Continent and in the United States, a unit with fifteen ciphers annexed; according to the English notation, the number produced by involving a million to the fourth power, or the number represented by a unit with twenty-four ciphers annexed. See the Note under Numeration. See: Numeration