"Big hat, no cattle” (or “all hat, no cattle") means someone who boasts a lot ("talks out of one’s hat), but doesn’t have the means to back it up.


28 June 1952, Albuquerque (NM) Times, pg. 4, col. 2:
“Big Hat, No Cattle”
(...)
Somehow this situation reminds us of the loud-talking ranchman who applied to a western banker for a loan. The banker asked a neighboring Indian if he regarded the rancher as a good credit risk. The chief pondered the question a moment, and replied:

“Big hat, no cattle.”

27 August 1961, Washington Post, pg. E1:
Rep. David T. Martin (R.-Neb.) reports another barbed one: How an Oklahoma Indian defines a New Frontiersman:

“Big hat—no cattle.”

Needless to say, this kind of irreverence is confined pretty much to the Republican corner.

8 July 1977, Chicago Tribune, pg. C1:
“The guy’s nothing but a nickel-and-dime politician. ... a Texan—big hat and no cattle.”
(Charles O. Finley, owner of baseball’s Oakland A’s—ed.)