say it: DRED-fuh-lee
dreadfully is an adverb meaning "of a dreadful kind". It carries 2 recorded senses.
in a dreadful manner
“as he looks at the mess he has left behind he must wonder how the Brits so often managed to succeed in the kind of situation where he has so dismally failed”
Definitions, synonyms and semantic relations for dreadfully come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.