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.
от bunkbuddies 09 май 2010
2 more definitions
Where a group of Multicultral people wank each other off (in a whole group)
Rainbow wank is my good friend
от Bitch man 06 август 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.
от Wet Wet Wet Wet 19 август 2010