From Longman Dictionary of Contemporary Englishbe all talkbe all talkspokenBOASTDO something/TAKE ACTION someone who is all talk talks a lot about what they intend to do, but never actually does it →talk
Examples from the Corpus
be all talk• Ralph's all talk. I wouldn't take him too seriously if I were you.• Britain is all talk and no action.• The right Hon. Gentlemanis all talk and no fight.• Until yesterday it was all talk.• His criticsleaped on his decision not to run, saying that Kemp was all talk and no action.• Revivalis all talk LET'S be honest about it, the great Kendall revival is not going to happen.