The phrase "an unreasonably" is grammatically correct and can be used in written English.
It is typically used to modify an adjective and express that something is being done or said in an unreasonable manner. Example: He stormed out of the room in an unreasonably angry manner, slamming the door behind him.
An example would be an unreasonably large correlation between the temperature at two distant locations on the globe.
An unreasonably-priced star in an unreasonably priced car – Clarkson skittered across the screen for a few seconds, in what felt so much like the segue into the big proper interview we'd been promised.
Consider the question "What would it be reasonable for me personally to pay for the song of a nightingale, and for the reproductive strategy for genes that it represents?" An unreasonably large answer might be £1 million, and an unreasonably small one, 10 pence.
That is an unreasonably long interval.
Three years is an unreasonably long time in a child's life.
The price was an "unreasonably low valuation for Dynegy's assets," an analyst with JPMorgan Chase wrote.
"It presents an unreasonably rosy picture," said Mr. Hevesi, one of four Democrats running for mayor.
He told the Danish newspaper Berlingske: "Dan and his family have paid an unreasonably high price.
"It's not, like, the 'move to New York and have an unreasonably large apartment on an unreasonably cute street' version, but, like, hopefully feels real without feeling like a Mike Leigh movie," she says.
I waited for an unreasonably long time, long enough to realize that she wouldn't be back that day.
They were an heirloom variety, reintroduced by the food historian Glenn Roberts at Anson Mills — potent little field peas, possessed of an unreasonably rich brown broth.
