a horse's penis

it is a very long and quite retractable. when it extends, its over a foot long, and when it retracts, its nothing. it actually goes back inside the horse's body.

Adj. Something that is expected to have a long lifespan by virtue of having existed for a long time, based on the lindy effect, named for the New York restaurant Lindy's, coined by Albert Goldman and popularized by Nassim Taleb.