When a guy is making a sandwich for his lady friend(which rarely happens) and he has no cheese for the sandwich. What he does at this point is ejaculate onto the bread, using his"jizz" as cheese.
Guy:"Honey this is a once in a life time opportunity, I'm making you a sandwich, what do you want on it?"
Girl:"I don't care babe but I want it to be CHEESE-TASTIC!"
Used by the adolescent population at large to describe something so bloodycheesy, that it actually becomes amazingly fantastic. The use of the word cheesetastic usually implies a derived pleasure from the utter cheese of a situation or phrase.
Be cautious, large danger of over usage.
*watches soap opera in which lead actress is pregnant with the baby of her brother's wife's father's uncle, and is married to her father*
"Dude, her unfortunate pregnancy situation is so totally cheesetastic!"
The word cheesetastic is obviously a reference to an over the top enthusiasm for something. It is generally a sarcastic statement implying disbelief in the concept being enthused upon.