mdnf 

Taking a "massive" dump and not flushing it. Massive Dump, No Flush

I took a MDNF in the CEO’s private bathroom.

mdnf by Nathan November 9, 2004

mdnf 

the hipster way to say "my dick needs fucking"

often thrown into random conversations

"hey joe whats up"
"MDNF!!!"
"WTF does that mean?!?!"
"oh; you know ;"

mdnf by Simpy April 26, 2009

MDNF 

Acronym- Minors Do Not Follow
Used by Twitter accounts that post explicit content or are just not comfortable having to watch what they post because they have kids around.

The hornyposting account had MDNF listed in the name

MDNF by c0ca1n3c0wb0ys June 4, 2024