Very, exceedingly. This and the words awful, terrible, monstrous, &c., are indiscriminately used by uneducated people for the purpose of giving emphasis to an expression.
There was a swod of fine folks at Saratoga, and dreadful nice galls.--Maj. Downing's Letters, p. 35.
It's a fact, Major, the public has a dreadful cravin' appetite for books.--Ibid. May-day in N. Y., p. 4.
The young ladies thought Mr. Harley's new storekeeper a dreadful nice young man, if he hadn't such a horrid nose.--Chronicles of Pineville.
She was a dreadful good creature to work.--Mrs. Clavers.
It is used in the same way in England, in the Westmoreland and Cumberland dialects:
I send to this an, to tell thee amackily what dreadful fine things I saw i' th' road tuv at yon Dublin.--Poems and Glossary, p. 125.