The phrase "terrifying rate" is correct and usable in written English.
You can use it to describe something happening at a very rapid speed that causes fear or alarm. For example, "The forest fires are spreading at a terrifying rate, and it seems like nothing can stop them."
The charity said the "terrifying" rate of the spread of the disease was outstripping medical supplies and threatened a breakdown of Sierra Leone's already fragile health system.
"Our major museums are sliding at a terrifying rate down the international league table while the incentives to encourage private giving are insufficient," he said.
The Ecuadorian Amazon is disappearing at a mind-boggling and terrifying rate as illegal loggers and oil companies continue to destroy vast swathes of the forest.
Frances Crook, the chief executive of the Howard League for Penal Reform, warned of the "terrifying" rate of suicides in prisons and called on the government to rethink its plan, saying it will leave young prisoners in isolation for too many hours.
The outbreak has killed more then 3,000 people in West Africa - with the infection spreading at a "terrifying" rate.
Save the Children says Ebola is spreading across Sierra Leone at a "terrifying rate", with the number of new cases being recorded doubling every few weeks.
Erin Brockovich visits towns with terrifying rates of cancer, continuing the work that inspired the Oscar-winning film starring Julia Roberts (a few clips of which are shown).
Young black men are being shot by white police officers at accelerating, terrifying rates.
For all his military posturing, Mr Chávez, writes Mr Carroll, "carried a plastic sword".Someone with more repressive instincts might have done something about the country's terrifying murder rate.
People in this story are from Guatemala City, which has a terrifying murder rate because of incursions by drug gangs, and from the Guatemalan Highlands, where their elderly relatives are traditional Mayan healers.
Singing a cappella or accompanying himself sparsely on the concertina, Louis Killen was known for his lyrical tenor — a "terrifying decibel rate," as one British critic described it — and a haunting ability to capture the aching loss at the heart of many traditional songs.
