from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Displaying erratic behaviour
- n. A person who displays such behaviour
- n. Compound of genius and fool
from the GNU version of the Collaborative International Dictionary of English
- n. A person of congenitally abnormal mind bordering on insanity or degeneracy.
from The Century Dictionary and Cyclopedia
- n. One who exhibits symptoms of mental degeneration but is not positively insane; a semi-insane person; a crank: a term used by Lombroso to designate a semi-insane person whose ideas and aims (often of a literary or artistic character), while they may simulate those of talent and even of genius, are marked by radical absurdities which the patient is unable, through mental weakness, to perceive.
From Italian matto ("insane") + -oid ("likeness or resemblance"), from Ancient Greek εἶδος (eidos, "form") (Wiktionary)