Dicklantern
Noun - a crude dim light used in dark places such as a closet or the driver's seat of a vehicle on long car rides to locate one's belt,zipper,and genitals in order to masturbate. Used when other people are around that you do not want them to know you are masturbating.
Dude, I got so horny on that long car ride that I just had to rub one out. Thank god I had my trusty dicklantern