That which cannot be named. Used as a substitute for the name of an object that you don't know or that you have forgotten in the deep recesses of your mind. The word is usually preceded by a pause as you perform a mental search for the object's name... unsuccessfully.

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.