'crackpot' definitions:

Definition of 'crackpot'

(from WordNet)
noun
A whimsically eccentric person [syn: crackpot, crank, nut, nut case, fruitcake, screwball]

Definition of 'crackpot'

From: GCIDE
  • crackpot \crackpot\ n. a whimsically eccentric person.
  • Syn: crank, nut, nutcase, screwball. [WordNet 1.5]