1a ball of packed snow, especially one made for throwing at other people for fun:they pelted him with snowballs
a thing that grows rapidly in size, intensity, or importance:a public-debt snowball that could grow to American proportions [as modifier]:the closures are expected to have a snowball effect, impacting jobs and tax revenues
2a cocktail containing advocaat and lemonade.
3a dessert resembling a ball of snow, especially one containing or covered in ice cream.
1 [with object] throw snowballs at:I made sure the other kids stopped snowballing Celia
2 [no object] increase rapidly in size, intensity, or importance:the campaign was snowballing
a snowball's chance (in hell)
informal no chance at all:the scheme has a snowball’s chance in hell of being accepted