- 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.
Meaning of 'septillion' (Princeton's WordNet)
1 . septillion
[ n]
Meaning (1): - the number that is represented as a one followed by 24 zeros