When your having a really boring day at work and there is nothing else to do but add random words to urban dictionary and hope a customer walks throught the door and you can sell them a damn computer.
Fantastically crappy. Something or some situation so crappy that it is barely to be believed. Akin to calling something "fantastic" in a sarcastic voice.
I went to a concert last night, and the motherfucking, craptastic audience made so much goddamned noise that I couldn't hear the music.
When something both sucks and blows; when "fantastic" just can't be said ironically enough; when you're tired of saying, "That's just fucking great"; when you're tired of people saying you're too pessimistic for saying everything's crap so you pep things up with something that at least sounds more optimistic
Some person you dislike gets something you think you deserve: "That's craptastic!"
Or: "Have you seen the new reality TV show? Man, it's totally craptastic!"