Definition of "monomaniac"
monomaniac
noun
plural monomaniacs
A person who is obsessed with a single thing, to the exclusion of other concerns.
Quotations
To talk nonsense, or poetry, or the dash between the two, in a tone of profound sincerity, and to enunciate solemn discordances with received opinion so seriously as to convey the impression of a spiritual insight, is the peculiar gift by which monomaniacs, having first persuaded themselves, contrive to influence their neighbours, and through them to make conquest of a good half of the world, for good or for ill.
1859, George Meredith, chapter 15, in The Ordeal of Richard Feverel. A History of Father and Son. […], volumes (please specify |volume=I to III), London: Chapman and Hall
adjective
Focused on one thing above all others.
Quotations
...then it was that monomaniac Ahab, furious with this tantalizing vicinity of his foe, which placed him all alive and helpless in the very jaws he hated; frenzied with all this, he seized the long bone with his naked hands, and wildly strove to wrench it from its gripe.
1851 November 14, Herman Melville, chapter 133, in Moby-Dick; or, The Whale, 1st American edition, New York, N.Y.: Harper & Brothers; London: Richard Bentley