The Collaborative International Dictionary
Mattoid
Mattoid \Mat"toid\, n. [It. matto mad (cf. L. mattus, matus, drunk) + -oid.] A person of congenitally abnormal mind bordering on insanity or degeneracy.
Wiktionary
mattoid
a. Displaying erratic behaviour n. 1 A person who displays such behaviour; a person of congenitally abnormal mind bordering on insanity or degeneracy. 2 Compound of genius and fool. (rfex)