- a story that cannot be believed easily
- something that is made up to be out of the plausibility range.
- a story making claims that is based on untrue facts making something look bigger than it is, that is, an exaggerated story
- You cannot believe everything he says since most of them are just tall stories.
- That is such a tall story because it has been passed down in generations and every one added something of their own to it. Now, when one hears it, it sounds legendary.
The origination comes from boastfulness which was meant to either deceive or just amuse people. In the 1900's these kind of stories were known as Munchausens which was named after an actual person. He was popular because he would always have extravagant stories about himself. In the United States, tall stories were the tales that were told and retold around the campfire. It usually involved mythical characters achieving larger than life tasks.
In the literary world, the phrase was first used in 1670 in 'The Grounds & Occasions of the Contempt of the Clergy' by John Eachard. This became more popular 1869 in Routledge's Every Boy's Annual which used the phrase as it is meant today.