An abbreviation for "darn tootin fun", use this around millennials to gain their trust and friendship.
"darn tootin fun" originates from an episode of the popularsitcom "Friends" which teens today love.
Son: Hey dad I'm kinda bored, you wanna do something?
Dad: I'm feeling DTF
Son: Alright let's go get in the hot tub!
Dad: Maybe I'll even let you taste my cum!
Son: Really? Coke and rum?
Dad: Yeah... sure
Immediate meaning of DTF is Down To Fuck however it has become a 'call to arms' for a night out.
Friday night: Jimmy - Lads who is DTF tonight.
Sean - Sorry guys I have sand in my vigina and can't come out (hence not DTF)
Everyone else - I am way DTF (displaying an extreme level of DTF, hence is willing to go out, drink alcohol and try to pick up birds)