1
general::
Phrase(s): *blind as a bat
1. completely blind. (Bats are not really blind. *Also: as ~.) • He lost his sight in an accident and is as blind as a bat. 2. not able to see well. • I’m as blind as a bat without my glasses. 3. unwilling to recognize problems or bad things. • Connie is blind as a bat when it comes to her daughter’s disgraceful behavior.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Quite blind; also, unaware. For example, Without my glasses I'm blind as a bat, or I had no idea they wanted me to take over his job; I was blind as a bat. This simile, based on the erroneous idea that the bat's erratic flight means it cannot see properly, has survived even though it is now known that bats have a sophisticated built-in sonar system. [Late 1500s]
American Heritage Idioms