'Septillion' definitions:

Definition of 'septillion'

(from WordNet)
noun
The number that is represented as a one followed by 24 zeros

Definition of 'Septillion'

From: GCIDE
  • Septillion \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. [1913 Webster]