When you masturbate for so long there is blood from chaffing, by the time you ejaculate the semen will be mixed with blood.
Dude I was masturbating for so long last night I gave myself a rainbow wank.
av bunkbuddies 9 maj 2010
2 more definitions
Where a group of Multicultral people wank each other off (in a whole group)
Rainbow wank is my good friend
av Bitch man 6 augusti 2006
When you kneel on the floor, pants down, cock in hand, then lay out all your favourite porn mags on your preferred climax pages in a rainbow shape around you and then have a wank.
My Mum walked in on me having a rainbow wank last night! I couldn't hide the porn mags quick enough.
av Wet Wet Wet Wet 19 augusti 2010