I. snow ‧ ball 1 /ˈsnəʊbɔːl $ ˈsnoʊbɒːl/ BrE AmE noun [countable]
1 . a ball of snow that children make and throw at each other:
We had a massive snowball fight.
2 . snowball effect if something has a snowball effect, it starts a series of events or changes that all happen because of each other
3 . not have a snowball’s chance in hell informal to have no chance at all
II. snowball 2 BrE AmE verb [intransitive]
if a plan, problem, business etc snowballs, it grows bigger at a faster and faster rate:
Interest in the sport is snowballing.