It's just a term used - mostly with option traders to describe big moves (some people have definitions for the move but there is no formal definition). I see it a lot with Bitcoin used to describe large candlestick moves.

Omega measures the percentage change in an option's value with respect to the percentage change in the underlying price. So when a big move happens someone may say, "We gettin' a [big] Omega move today!" With options trading you can have massive moves either way.