A person suffering from monomania.

Roget 504: madman, lunatic, maniac, bedlamite^†, candidate for Bedlam, raver^†, madcap, crazy; energumen^†; automaniac^†, monomaniac, dipsomaniac, kleptomaniac; hypochondriac etc. (low spirits);; crank, Tom o'Bedlam.    dreamer etc. 515; rhapsodist, seer, highflier^†, enthusiast, fanatic, fanatico [Sp.]; exalte [Fr.]; knight errant, Don Quixote.    idiot etc. 501.    ... show more

Polish: monoman