twenty-twenty definition by American Heritage Dictionary
The American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Having normal visual acuity.
Origin: From a method of testing vision by reading charts at a distance of 20 feet.
twenty-twenty - Science Definition
Having normal visual acuity. A person with twenty-twenty vision can see type as small as one-third of an inch at a distance of twenty feet.