Sep*til"lion (?), n. [F. septilion, formed fr. L. septem seven, in imitation of million.] According to the French method of numeration (which is followed also in the United States), the number expressed by a unit with twenty-four ciphers annexed. According to the English method, the number expressed by a unit with forty-two ciphers annexed. See Numeration.

Sep*til"lion (?), n. [F. septilion, formed fr. L. septem seven, in imitation of million.] According to the French method of numeration (which is followed also in the United States), the number expressed by a unit with twenty-four ciphers annexed. According to the English method, the number expressed by a unit with forty-two ciphers annexed. See Numeration.

• Usually means a trillion trillion or a billion billion million, That is to say, a 1 followed by 24 zeros, 1024
  
• (Dated usage, notably British) A billion quintllion or a 1 followed by 42 zeros, 1042