An unimpressive person who regularly has daydreams of glory: Walter Cronkite is a Walter Mitty in reverse
[1939+; fr the title character in The Secret Life of Walter Mitty, a story by James Thurber]
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with Walter Mitty
A person, generally quite ordinary or ineffectual, who indulges in fantastic daydreams of personal triumphs. For example, He's a Walter Mitty about riding in a rodeo but is actually afraid of horses. This term comes from James Thurber's short story, The Secret Life of Walter Mitty (1939), describing just such a character.