To vomit mass quantities of large solid material. Very unpleasant but could be worse. See example.
Barfly: "I went home totally drunk from the bar last night and started blowing chunks."
Bartender: "That happens when you're shitfaced sometimes."
Barfly: "You don't understand. Chunks is the name of my dog."
When a woman snowballs you (I.e pretends to swallow your cum and spits it back into your mouth when she kisses you) and it backfires as you thereafter projectile into her open mouth. The resultant mixture is a combination of cum and vomit.
Claire: Ah I tried to snowball Anthony last night but it backfired and he gave me a chunky snow dragon!!!
Olivia: ah no ways, the same thing happened to me last night!!