Countable noun, chiefly historical/literary, as in "penny dreadful"; occasionally used in plural "dreadfuls".
Definitions
A sensational or cheaply produced story, magazine, or novel, especially a nineteenth-century 'penny dreadful'. Victorian readers gobbled up the lurid dreadfuls sold on street corners.
Informal/colloquial intensifier usage, chiefly British
Definitions
Used informally as an intensifier meaning "very" or "extremely". I'm dreadful sorry for the inconvenience.