look up any word, like bukkake:
 
1.
Giving oral pleasure after the receipt of an unexpected gift.
Hillary received a beautiful engagement ring. Right after, she was caught on camera duffing her boyfriend on the barcalounger.
by Opeth1429 February 26, 2010
 
2.
The act of living with the bare minimum required to maintain the ultimate bachelor lifestyle.

Those "duffing it", often live in an environment that only a true single man could tolerate. Normal living spaces may be converted for storage of motorcycles, beds may not have ever worn sheets, dishes may be piled up waiting for execution via the trash can.
Oh man Bobby is duffing it, he has a guitar stand where his dining table should go.
by billystalker May 03, 2011
 
3.
Farting slow.
When you have to let out a fart so bad but you are afraid it will be loud enough for everyone to hear at the DMV, church, or at your boyfriend's or girlfriend's family dinner. So you duff it..you let it out slowly.
"I'm duffing right now and no one even knows!"
by siscossilverhair August 05, 2014