Well, apart from meaning a ball of snow, such as might be thrown by children at each other for fun. Really, that's where my mind went with the word 'snowball', much like the rest of the anglophone world. Yes, there may be slang and other juvenile repurposings of the word, but in normal, everyday (well, wintertime everyday) usage snowball means exactly what the OED says it means. Not sure why anyone would imagine otherwise?
http://www.urbandictionary.com/define.php?term=snowball
Reminiscent of when Microsoft called an overlay dialog a "floater" and all the South Africans and Brits in the room started laughing.
http://www.urbandictionary.com/define.php?term=floater (the 2nd definition)