The black crusty stuff that forms around the top of a ketchup bottle.
Would you like some flen with those fries?
by Rich Hall February 21, 2003
From Swedish, meaning dick-ckeese. You know, that yellow stuff on your cock.
Man, there's a lot of flens on my dick. I knew I should've cleaned my penis at least once a year.
by Trev January 17, 2005