A horrific event in which one is slammed in the face with such a considerable and inordinate payload of semen that their universe is forever chang-ed.
1) If i ever ran into Brooke Burke on the street, i would drop trou and she would be the direct object of the greatest cumtastrophe the world has ever seen.
2) Sometimes, I just want to go to a Japanese massage parlor. Only problem is...because i love asian women so much, when I get the happy ending, it usually turns into a cumtastrophe.
When something is so nice that it gives you the urge to cum on it with extreme vigor and force. These things can include but are not limited to wedding dresses, food, and white people.
You: "Dude that wedding dress is so cumtastical that I'm exploding in my pants just thinking about all the fabric I can ruin in one blow!"
Friend: "What in the actual fuck is wrong with you?"