The phrase "deadly boring" is correct and can be used in written English.
It is typically used to describe something that is extremely boring or dull. Example: "The professor's lecture was deadly boring, putting most of the class to sleep."
They are deadly, deadly boring and Beckett would have hated them.
Also appearing are the deadly boring Our Lady Peace, the more promising Eve Six, and the as-yet unknown Outcry.
A few years ago, it was unthinkable that a country would go bust, making the sovereign bond market deadly boring.
But his good friends say it was because he sometimes was so deadly boring that he could induce sleep in colleagues.
"There's only one thing more deadly boring than listening to other people's dreams," she interrupts, "and that is listening to other people's problems".
Nor was it as "excellent" as it claimed to be, he said, and performances sometimes looked like "wallpaper … and were deadly boring".
As is Handler's remarkable presentation of an adolescent girl's point of view: at one moment, during a deadly-boring-to-her basketball game, Min wonders wryly just what is keeping her in the relationship, while at another, her responses to Ed's amorous attentions make it very, very clear.
And thank goodness – otherwise we would have evolved to be a deadly-boring species which never wanted to get lost, never tried things to just see what happened or did things for the hell of it.
Stuart Hampshire remembered more of the boudoir politicking than of the debates themselves (which were, according to Hannah Arendt, 'deadly boring').... Sidney Hook's bedroom became the focus of a cell opposed to Dwight's appointment.
The most common reaction was that while Colton may be a nice guy, he's extremely boring — a deadly ingredient in any reality show.
It was the first time we felt really close, carefree together, high on the sheer joy of getting away from our mother; the deadly dinner parties of political bores, the Sunday lunches for the same people that lasted hours, Jackie and I not allowed to say a word.
