D defs.my
Entry 1 sense Webster, 1913

Trillion

/trĭl'yən/ · Tril·lion · IPA /ˈtɹɪ(l)jən/
01 n. According to the French notation, which is used upon the Continent generally and in the United States, the number expressed by a unit with …
  1. 1.
    According to the French notation, which is used upon the Continent generally and in the United States, the number expressed by a unit with twelve ciphers annexed; a million millions; according to the English notation, the number produced by involving a million to the third power, or the number represented by a unit with eighteen ciphers annexed. See the Note under Numeration. See: Numeration