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1.
MDF
A semi-erect penis.

Name after the building material of the that name (Medium Density Fibreboard) which is "not quite wood".
She was not an attractive lady. When it came to performing my gentleman's duties all I could muster was a poor MDF.
by Adeybaby January 08, 2004
 
2.
MDF
Mini Dildo Forking, the act of sticking a mini dildo onto a fork then placing them in a formation on someones lawn. When the wind blows the dildos sway in the wind. Penises in the wind.
oh shit there are swaying penises in my lawn. looks like i got MDFed.
by MDF master January 18, 2011
 
3.
MDF
my dear friend
Hey, thanks MDF!
by thegreatme November 29, 2009
 
4.
MDF
MDF stands for Most Defiantely Fuckable, also a MLG Halo 2 Team ran by Brandon in Illinois
*Hot Girls Walks By*
Old Man:Damnnn That Girl Is MDF come Here Sweeeeetie
by MDFBrandon March 08, 2007