blind as a bat

Idioms  

1. 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]

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Example Sentences

“I was blind as a bat, but I always knew where the target was,” Cooper says.

From The New Yorker • Sep. 30, 2019

I don't understand this "trademark" thing – Larkin didn't wear spectacles for effect; he was as blind as a bat – and I think he would have found this irredeemably gruesome.

From The Guardian • Jun. 26, 2010

She has to learn her roles letter-perfect, and for a good reason: "I'm as blind as a bat."

From Time Magazine Archive

The old Shaper, a man I cannot help but admire, goes out the back window with his harp at a single bound, though blind as a bat.

From "Grendel" by John Gardner

It was, as you say, damned awkward about his being blind as a bat; in fact, I was put to quite a lot of trouble getting the agreement witnessed.

From A Man in the Open by Pocock, Roger