As measured or indicated by, on the basis of. For example, How far is it in terms of miles? This usage originated in mathematics, where it alludes to numerical units. [Mid-1700s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.