crank letter

noun

1. a hostile or fanatical letter, often sent anonymously.

Idioms and Phrases

Also, crank call. An irrational, fanatical, or hostile letter or telephone call. For example, The office was flooded with mail, including a lot of crank letters, or Harriet was upset enough by the crank calls to notify the police. This expression employs crank in the sense of “irrational person.” The first term dates from the mid-1900s, the variant from the 1960s.

Example Sentences

A crank letter to the mayor insisted the turtle's attack on an Achilles tendon, of all things, reflected its outrage over Europe's bailout of Greece.

Read more on The Wall Street Journal

It was published by a tabloid newspaper as a sort of gag––a strange crank letter.

Read more on Project Gutenberg

Under the heading "How Incidents Are Investigated," the Project "Saucer" report says: But the hoaxes and crank letters in reality play a small part in Project "Saucer."

Read more on Project Gutenberg