crackpot(n = noun.person) crank, fruitcake, nut, nut case, screwball - a whimsically eccentric person;
is a kind of eccentric, eccentric person, flake, geek, oddball
a whimsically eccentric person. [WordNet 1.5]
crackpot, n. & adj. sl.
--n. an eccentric or impractical person.
--adj. mad, unworkable (a crackpot scheme).