1. The cardinal number equal to 7 × 10.
2. seventies
   1. A decade or the numbers from 70 to 79: They became grandparents in their seventies. The temperature hovered in the seventies.
   2. often Seventies The decade from 70 to 79 in a century.

[Middle English, from Old English -seofontig (in hundseofontig, the decad seventy, seventy).]

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.