What is the meaning of trillion?

noun

• A very large indefinite number (usually hyperbole. )
  • usage: "there were millions of flies"
  • synonyms: million, billion, zillion, jillion, gazillion
• The number that is represented as a one followed by 18 zeros.
  • usage: "in England they call a quintillion a trillion"
  • synonyms: one million million million
• The number that is represented as a one followed by 12 zeros.
  • usage: "in England they call a trillion a billion"
  • synonyms: one million million, 1000000000000

adjective

• One quintillion in Great Britain.
• One million million in the United States. .