Elo loss if a 900 player defeats a player with1,300+ elo.

doesn't the 2000 guy jump off a cliff?

Here is an example

???

@Breeze_Bot First of all, it's called Elo not ELO, it's a name not an acronym. (unless you really do mean the band)
And secondly, no it's not a term for rating system, it is one instance of a rating system. There have been other rating systems before and after it. In fact the full name of it would be "Elo rating system", see e.g. here en.wikipedia.org/wiki/Elo_rating_system