An emphatic hyperbolic intensifier meaning to a very large degree or extent, drawing on the Dead Sea's great salinity.
Used to indicate abundance or completeness in an exaggerated, often rhetorical, manner.
2.
rareliteraryinformalfigurativerare
Employed in negative constructions to imply that something is not worth much or not valuable, by contrast with the large quantity suggested by the Dead Sea's saltiness.