A more colorful term for butt hole or anus. It can also be used as an insult.
"Why does my breath smell like crap?"
"Because I rubbed your toothbrush on my doodoo cave."
"Why did you eat my last ice cream sandwich?"
"Because you're a doo doo cave who does not deserve such a tasty treat."
1.) A person who is such a jerk that they surpass the rank of 'asshole' and deserve to be called a 'Blunthole.'
2.) Another term for 'taint.'
"Did you eat my last Hot Pocket?"
"Yeah."
"Why you gotta be such a blunthole?"