ETYM French trillion, formed from the pref. tri- in imitation of million a million. Related to Billion.
An indeterminately large number.
1. (In Britain and Germany) The number that is represented as a one followed by 18 zeros; SYN. one million million million.
2. (In the United States and France) The number that is represented as a one followed by 12 zeros; SYN. one million million, 1000000000000.

A million billions (10^18); (American and French) a thousand billions (10^12).
(U.S.) One million million; (Britain) one quintillion; SYN. a trillion.