Anything said or done that is considered uncool or against all that is good in the world. Any person that has commited a blasphemy is afterwards subjected to a blasphemy slap
Lola: "Oh my God! There's a marathon of Hannah Montana coming on tonight! Wanna watch?"
Jim: "Hey man, did you hear that they're already making another Smash Bros.?"
Jim: "Yeah, but it's only being made for Playstation."
Al: "Blasphemy! They get all the good games!"
The slap given after one has commited a blasphemy
, to discourage it's continued use.
Rick: "Dude, Jonas just told me that he hates Guitar Hero!"
Rob: "You called blasphemy on him right?"
Rick: "Hell yeah I did, and he got a blasphemy slap to teach him a lesson."