What does 'all hat and no trousers' mean?

[Priya Raghavan]

English Language Tests, Intermediate level

ESL/EFL Test #302 "English Slang Idioms (24)", question 3

"Oh, he says he will get that new job but he is all hat and no .......... He isn't qualified but thinks that he is likeable enough to charm anyone into anything," Sally told Lucy.

(a) trousers
(b) rain
(c) purpose
(d) bolts

English Language Tests, Intermediate level

ESL/EFL Test #302 "English Slang Idioms (24)", answer 3

"Oh, he says he will get that new job but he is all hat and no trousers. He isn't qualified but thinks that he is likeable enough to charm anyone into anything," Sally told Lucy.

Correct answer: (a) trousers

Your answer was: incorrect
"Oh, he says he will get that new job but he is all hat and no purpose. He isn't qualified but thinks that he is likeable enough to charm anyone into anything," Sally told Lucy.
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What does 'all hat and no trousers' mean? Is it same as 'all hat and no cattle (an earlier test)'?

Priya Raghavan

[Mister Micawber]

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Yes, that's right:

all hat and no cattle

1. (US, idiomatic) Full of big talk but lacking action, power, or substance; pretentious.

all hat and no trousers

"All talk and no action", "All bark and no bite". One who seems to be great but is of little substance.
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Native English teacher at Mister Micawber's