What is the meaning of billion?

noun

• The number that is represented as a one followed by 12 zeros; in the United Kingdom the usage followed in the United States is frequently seen.
  • synonyms: one million million, 1000000000000
• A very large indefinite number (usually hyperbole. )
  • usage: "there were millions of flies"
  • synonyms: million, trillion, zillion, jillion, gazillion
• The number that is represented as a one followed by 9 zeros.
  • synonyms: one thousand million, 1000000000

adjective

• Denoting a quantity consisting of one thousand million items or units in the United States.
• Denoting a quantity consisting of one million million items or units in Great Britain. .