A cross between "smash" and "crunch" denoting the demolishing of an entity, however is not neccessarily limited to the physical,rather it can also be used post-verbal-crucifixion, adding to the diminishment of he/she/s dignity.
"Man, Fred's parents had a black baby..."
"Their Both white"...."smunched!"
Freds dad = Smunched!
Smunching is what happens when you have a boner and see something so unattractive and disturbing it immediately makes your boner go limp. This is not a gradual softening of the penis, this is going from 12 to 6 instantly. This terrible sight has smunched your boner.
You have a boner, you see your grandma taking a shit, you instantly don't have a boner...you've been smunched.