"Puffery" is a legal term used to describe a defense used against charges of fraud or breach of contract. In this defense, the defendant argues that claims made (typically in advertising) are so extravagant or so subjective, that no reasonable person would take them seriously, and thus constitute "mere puff" rather than fraudulent claims. Examples might include "the world's best fried chicken," "America's favorite beer," Coca-Cola's representation that polar bears drink its product, or Energizer claiming that the Energizer Bunny "keeps going and going and going" even though in reality Energizer batteries do, in fact, eventually go dead.
The defense originates from the infamous "Carbolic Smoke Ball" case of 1893, in which the Carbolic Smoke Ball Company argued that their claims that their smoke ball would prevent influenza were just "a puff." Although the puffery defense actually failed in this case, it has since been used successfully in a wide variety of instances.
The concept of puffery was enshrined in US trade policy in 1957 when customers complained to the Federal Trade Commission about a store that advertised the "world's lowest prices." The store argued puffery and the FTC agreed, officially defining "puffery" as a "term frequently used to denote the exaggerations reasonably to be expected of a seller as to the degree of quality of his product, the truth or falsity of which cannot be precisely determined."