1. "Christian" + "asshole". Typically referring to a Christian who believes he/she is genetically, ethnically, morally and spiritually superior to all other races and religions. This person thinks in terms of moral absolutes, to the effect of "us good, them bad," and presumes anyone who looks, thinks, or acts different from him/herself to have been put on earth by Satan himself for the purpose of spreading degeneracy. He/she is unwilling to compromise any of his/her beliefs the slightest bit, but the first to criticize others for being hardheaded. He/she thinks everyone is going to Hell who doesn't hate non-Americans, liberals, gays and lesbians, poor people, planned parenthood, evolution, Jews, Muslims, etc. But he/she also thinks one can buy one's way into Heaven by donating generously to the Republican Party. In the face of overwhelming evidence against his/her beliefs, he/she will immediately run from the conversation, usually with an excuse to the effect that "I don't have to listen to you because God's on my side and I'm better than you."
2. The supposed orifice on such a person's body from which their self-righteous and ignorant bullshit is excreted.
"Pat Robertson is such a christhole."
"Hey man, I smell something. Did you forget to wipe your christhole?"