trillion trillion /ˈtrɪljən/

adjective

1. One million million in the United States  ( trillion )
   one million million in the United States
   
2. One quintillion in Great Britain  ( trillion )
   one quintillion in Great Britain
   

noun

1. The number that is represented as a one followed by 12 zeros  ( 1000000000000 , one million million , trillion )
   the number that is represented as a one followed by 12 zeros
    In England they call a trillion a billion
   in England they call a trillion a billion
   
2. The number that is represented as a one followed by 18 zeros  ( one million million million , trillion )
   the number that is represented as a one followed by 18 zeros
    In England they call a quintillion a trillion
   in England they call a quintillion a trillion
   
3. [Informal] A very large indefinite number (usually hyperbole)  ( bazillion [Informal, N. American] , billion [Informal] , gazillion [Informal] , jillion [Informal, N. American] , million [Informal] , trillion [Informal] , zillion [Informal] )
   a very large indefinite number (usually hyperbole)
    There were millions of flies
   there were millions of flies