One who is so obsessive of being a Christian that they incorporate it into anything. Holy hippies will often wear shirts with phrases such as "He Saves" an lanyard with WWJD (What Would Jesus Do) and wearing bead necklaces with crosses on the end, even if they are guys (note they aren't gay because that would defy the Bible). They will bring up what their Bible study classes tell them if you even mention anything not within limits of the bible.
Person 1: Aw that chick is so f**king hot!
Holy Hippy 1: Dude think of the bible man, don't cuss...
Holy Hippy 2: Yeah WWJD?