SNOWBALL

? Like the phrase: "HOLY SHET HEIMERDINGER IS SNOWBALLED SO HARD, PLES REPORT EVERYONE IN THE WORLD" Or the phrase: "The snowball feature in the Legend of The PoroKing is great!!!! :D :D :D :D :D :D :D"

Snowballing (the first phrase) is when a champion gets a few kills, which gives them a huge advantage. Basically like, once they start with kills, they won't stop, hence, snowballing. And the second snowball phrase; well, that's kinda obvious

I assume you mean the Legendary Snowball event. Right now, anytime you receive a Legendary skin, you will receive a free mystery gift from Riot, and if that free mystery gift is another Legendary skin, you will receive another, and you will keep receiving free mystery gifts until you receive one that isn't a Legendary skin. It doesn't matter how you receive the initial Legendary skin either; you can buy it for yourself or you can be gifted one, either normal gift or mystery gift, by a friend. All of this also applies to the 3 Ultimate skins as well.

Here's a link for it: http://na.leagueoflegends.com/en/page/look-out-its-snowdown#legendary