Definition of "Trillion" :

noun: the number that is represented as a one followed by 12 zeros

"In England they call a trillion a billion."

noun: the number that is represented as a one followed by 18 zeros

"In England they call a quintillion a trillion."

noun: a very large indefinite number (usually hyperbole)

adjective: one million million in the United States

adjective: one quintillion in Great Britain