Noun

• S: (n) billion, one million million, 1000000000000 (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)
• S: (n) million, billion, trillion, zillion, jillion, gazillion, bazillion (a very large indefinite number (usually hyperbole)) "there were millions of flies"
• S: (n) billion, one thousand million, 1000000000 (the number that is represented as a one followed by 9 zeros)

Adjective

• S: (adj) billion (denoting a quantity consisting of one thousand million items or units in the United States)
• S: (adj) billion (denoting a quantity consisting of one million million items or units in Great Britain)