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1. A severe mentally instable individual

2. A homicidal psychotic

3. Describing any event or action as very crazy or extremely insane

4. Saying "fucking nut" with emotional outburst or humorous purpose

5. The sexual act between 2 nuts or more.
You gotta be futnut if you wanna jump off the cliff!!!

He's a real futnut, watch out or he'll kill you!

Standing naked on top of Washington Moument is definitely futnut!
by Troy T October 13, 2005
Short for (or code for) the term fucknut. Can be used when cursing isn't appropriate.
That dumb futnut just cut off three cars while drinking a beer.
by futnuts June 26, 2010