1. A joke that completely kills a chain of building jokes, rendering the comedic banter obsolete.

2. A joke that is so far out of left field, that it causes all participants to question their friendships and ultimate self worth.

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.