The word "Rape Shower" which is the actual act of taking a shower because you feel so ashamed.
Even though "servicing himself" was very pleasurable, Jason could not oversomce his shame for what he had done to his body, so he tried to "clean" himself with a rape shower, but nothing could bring back his hand's virginity.
The act of showering or bathing following a particularly traumatic event in an attempt to wash away all physical and emotional traces of the horror just experienced. Typically effected in a foetal position, huddled in a corner of the shower stall, whilst weeping and limply rubbing a bar of soap over one's body as the scalding hot water mixes with the tears running down one's cheeks.
I'm not saying that this is the absolute goddam f***ing worst job I've ever had in my life, but the first thing I'm doing after I quit is go home to take a rape shower.