crank
n. countablen. a person who has very strange or unusual ideas that most people think are wrong. They often talk about their opinions a lot and try to convince others.
n. an eccentric person, especially one who is obsessively preoccupied with an unconventional or delusional theory. Often carries a pejorative connotation in academic or social contexts.
He is a bit of a crank when it comes to his theories.
The editor receives dozens of letters from every local crank who believes they have discovered a secret code in the newspaper.
While history occasionally vindicates the outsider, most scientific institutions must filter out the constant stream of manifestos sent by every self-taught crank claiming to have debunked the laws of thermodynamics.
From Dutch or Low German krank, ultimately from Proto-West Germanic krank, from Proto-Germanic krangaz, *krankaz (“bent; weak”). Cognate with Scots crank, krank, German krank (“sick”).
From Middle English crank, cronk, from a shortening of Old English crancstæf (“weaving tool, crank”, literally “bent or crooked staff”), the first element ultimately related to Etymology 1 above.
Commonly used as a mild insult for someone with fringe beliefs.