look up any word, like dirty sanchez:
 
1.
Fuck + Pictonary. A fun family game to play with all ages. The players (2- Infinite). Pick a Graphic (XXX rated) film or magazine and copy exactly a extravagant position that is performed.
Husband: Hey Hon! The kids are gone. Lets play some Fucktionary!
Wife:Oh yea! Lets play sweetie!

Boyfriend: Hey babe... want to play some Fucktionary.
Girlfriend: OMG! Totally... lets do it!
by The Zunk December 15, 2010
 
2.
The proper name for a dictionary that doesn't contain the word you are looking for..
"This dictionary doesn't have 'Honorificabilitudinitatibus' what the hell?"

"It's not a dictionary then, it's a Fucktionary."
by Leijona Sisu September 27, 2011
 
3.
A dictionary that has only words relating to the practice of sexual intercourse.
"GUYS! I NEED TO DEFINE THIS WORD! WHERE'S THE FUCKTIONARY?!"

Or

Kid 1: "Guys, what's a clitoris?"
Everyone in the world: "GET THAT KID A FUCKTIONARY!"
by Seiboobanigav November 13, 2010