noun
misdirected claim; incomprehensible idea
Jocular, humorous term; a pun on 名説 (famous theory). Used to describe a claim or idea that is off the mark or hard to understand.
See also: 名説
彼の迷説には誰もついていけなかった。
Nobody could follow his incomprehensible idea.
それは迷説というより、ただの勘違いだ。
That's not so much a misdirected claim as just a misunderstanding.