young, dumb and full of cum is referring to girls who are find their snatch is cum filled to the brim after a night on the town being shared around.

These particular sluts don't use protection and are too dumb to know better or care.
These girls often view their STD's as trophies confirming their sexual promiscuity status as rock star, collecting them like a girl guide collects badges for her sash and status.
After falling pregnant as a result of spontaneously hosting a (Bukkake) Jenny finds herself unsure who the father out of the 15 guys whose (loads) she took like cannonballs to her cunt.

In (hindsight) she agrees that she was young, dumb and full of cum that night.
by rapunzabel September 15, 2016
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