ˌtwenty-ˈtwenty BrE AmE , 20/20 noun [uncountable]
[ Date: 1800-1900 ; Origin: From normal sight being judged on the ability to read letters at a distance of 20 feet ]
1 . twenty-twenty vision the ability to see things normally, without needing glasses:
A pilot must have twenty-twenty vision.
2 . twenty-twenty hindsight used to say that it is easy to know what you should have done in a situation after it has happened, but you did not know what to do earlier