1. The cardinal number equal to 10¹².
2. Chiefly British. The cardinal number equal to 10¹⁸.

[French : tri-, third power (from Latin tri-, tri-) + (m)illion, million (from Old French milion; see million).]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.