hen's tooth

== English == === Etymology === Example of a jocularly non-existent phenomenon, as many birds lack any teeth (having developed a bill instead). Compare horsefeathers and when pigs fly. === Pronunciation === === Noun === hen's tooth (plural hen's teeth or hens' teeth) (idiomatic) Anything not naturally occurring. Synonyms: rocking horse shit; see also Thesaurus:rarity as rare as a hen's tooth ==== Translations ==== === See also === unobtanium