(adj.) descriptive of an entity or situation where something once small and relatively insignificant grows exponentially
at a swift pace, engulfing everything in its path. A more dramatic progression than the classic domino effect
. The basic workings of a literal snowball effect can be illustrated by taking one's average baseball-sized snowball and dropping it down the side of a snowy hill. As it descends it gathers more snow and whatever leaves, sticks, etc. are in its way. The snowball accumulates not only size, but speed until either the gigantic mass runs out of momentum, or collides with an immovable force.
A figurative description and example of its usage...
When Mortal Kombat
was first released, there were numerous instances of fans going to largely populated areas like college campuses and shopping malls, and yelling "MORTAL KOMBAT!!!" at the top of their lungs. Others within earshot who understood this cry would do the same. Depending on just how many "in the know" heard and participated, this created an amazing, echoing snowball effect.
Given that "the physics of snowballs being rolled down hills"
was never elaborated upon, for the moment one must accept that the above explanation should hold some merit.