A dirty gumper is when you poo in a plastic bag shake it up and spread it on your naked partner. Then you proceed to lick the remains off of your partner and have a dirty gumper make out
‘Hey dude we are out of ciggies so hit the ashtray, dunno what’s in there but just roll up a Forest Gumper n roll with it’
‘I’m so high. No smokes. Roll a Forest Gumper!’