Wiktionary
n. 1 A stereotypical fictional character whose focus on academic matters leads them to ignore or forget their surroundings. 2 (context by extension English) A person who tends to be oblivious to reality.
Wikipedia
The absent-minded professor is a stock character of popular fiction, usually portrayed as a talented academic whose focus on academic matters leads him or her to ignore or forget his or her surroundings.
The phrase "absent-minded professor" is also commonly used more generally in English to describe people who are so engrossed in their "own world" that they fail to keep track of their surroundings. It is a common stereotype that professors get so obsessed with their research that they pay little attention to anything else.
The stereotype is very old: the ancient Greek biographer Diogenes Laërtius wrote that the philosopher Thales walked at night with his eyes focused on the heavens and, as a result, fell down a well.
Usage examples of "absent-minded professor".
Then you know what he's like -- an elderly dodderer well over seventy, short-sighted, amiable, a typically absent-minded professor in every respect but one.
Lifting his hand to his head, the absent-minded Professor gravely felt and removed the little cocked hat, looked at it a minute, and then threw back his head and laughed like a merry bass viol.
Does a librarian with an eidetic memory feel superior to an absent-minded professor who won a Nobel Prize?
There is a story of an absent-minded professor who went up to his bedroom to change his tie before guests arrived.
I think there were literary models then of pure scientists and their absent-mindedness, and jokes about the absent-minded professor and all that, and many scientists gladly fell into this stereotype of absent-mindedness and indifference, including indifference as to what became of their discoveries.
I look at her sharply but she's got her innocent face on, the absent-minded professor musing over a theorem rather than focussing on the world, the flesh, and the devils of Interpol's most-wanted list.
He seemed to be an outright caricature of the absent-minded professor.
I saw a paunchy man of average height in his middle or late seventies with Mark Twain hair, dressed like an absent-minded professor whose wife has recently discovered LSD.
Carl Zolg had returned to his normal appearance of a somewhat absent-minded professor.
He wasn't merely observing or noting characters, as was his habit, but looking through them, past them, for one particular character, a Queer Duck dressed in black, with a walleye and an umbrella, a strange-gaited, long-haired, absent-minded professor sort of guy with funny shoes and a secret.
The man seemed to be working the absent-minded professor routine a little too much.