snowball effect

(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.