Similar to chode and taint. The raphe is the Samsonian destination between the nuts and schlong that provide men with all of their supreme macaroni boiling powers.
I let her lick my raphe after she gave me a nice blumpie.
Technically, raphe is a medically-appropriate term which refers to a ridge separating two lateral parts or organs. Examples of such ridges can be located on tongues and perinea.
Ideally, however, the term is used to describe the line that runs up the middle of your sack -- most likely to prevent your balls from flying out.
If someone unzipped my raphe, I'd go nuts.