" All bark and no bite "
Meaning:
Having lots to say but not willing to engage in a fight.
Example:
There's always one loud guy at the back who disappears when trouble starts - all bark but no bite.
Where did it originate?:
Britain, as a variant of 'his bark is worse than his bite', which is of early 19th century origin.
Where is it used?:
Hear the idiom spoken:
