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1.
Pen Fifteen, translated to pen15, then translated from leet, means penis. Used by sofisticated nerd everywhere
User name 'Pen fifteen'
OMG look @ his Pen Fifteen
by SensenmanN December 10, 2005
 
2.
a trick played on girls who are sweet, oblivious, innocent girls. a mean girl will ask them to join the pen club. she says"i'm pen 13, she's pen 14, and we want you to be pen 15. the girl, oblivious as she is, says ok! then the mean girl writes PEN15 or PENIS on the girl's hand.
that girl who played the pen fifteen trick is SO evil!!!!
by chinchilasrule February 14, 2008
 
3.
Pen15, literally penis.
"You remember those days back in third grade where I invited Kevin to join the Pen Fifteen club? So I wrote Pen15 on his hand and started lollerskatesing all over the place and he didn't get it. Then I told him to look at his hand and it looked like it said Penis. Hahaha, good ol' days, y0. w3rd. N shit.
Yeeeeeeeeeeeeeeeeeeeeeeah."
by BJ Streeby March 29, 2004