SCREWBALL
crazy, half-baked, screwball, softheaded
(adjective) foolish; totally unsound; “a crazy scheme”; “half-baked ideas”; “a screwball proposal without a prayer of working”
screwball
(noun) a pitch with reverse spin that curves toward the side of the plate from which it was thrown
crackpot, crank, nut, nut case, fruitcake, screwball
(noun) a whimsically eccentric person
Source: WordNet® 3.1
Etymology
Noun
screwball (plural screwballs)
(baseball) A pitch thrown with added pressure by the index finger and a twisting wrist motion resulting in a motion to the right when thrown by a right-handed pitcher.
(US) One who behaves in a crazy manner.
Adjective
screwball (comparative more screwball, superlative most screwball)
(originally US) Crazy, offbeat, bizarre, zany, or weird.
Source: Wiktionary