DARF is referred to as either a (1) "Drunk Ass Racing Fan" or a (2)"Dumb Ass Racing Fan".
In the case of "Drunk Ass Racing Fan", it refers to a fan who had too much to drink at a racing event and is now engaging in funny and embarrassing behavior you do not see from said person at a racing event when sober.
In the case of "Dumb Ass Racing Fan", it refers to fans, most commonly newer or "casual" ones, who thinks that every stupid change by racing series (i.e. NASCAR or Formula One) that upsets every fan with common sense is the best idea ever. They also tend to watch auto racing "only for the crashes" and will complain if there is no huge wreck. Recently this type of DARF has been observed to also to be commonly known and shown to be racist towards any ethnicity that is consider to be apart of the "white" race (Most commonly Caucasians & the Redneck people), sexist against females, discriminates against anything associated with the southern portion of the United States, agephobic against anyone over the age of 30, is pro-war and anti-peace, and has also been shown to be "phobic" in some manner; Whether it'd be homophobic, transphobic, or most commonly heterophobic. They also believe that any and all forms of discrimination should now be accepted in the sport, especially at the expenses of those they discriminate against, under the lie that they'll feel "more accepted" when in reality it's to run actual fans, especially those they discriminate against, out of the sport.
(1) Went to a race today and some guy three rows in front of me took off his shirt and started waving it like he was a strip-tease model when the cars went by cheering them on. He was an obvious DARF because he also had four cans of beer beforehand.
(2) DARF: "OMG! What an amazing race! I really loved it when 29 of the 34 drivers all crashed at the same time."
Actual Racing Fan: "Oh you're obviously a DARF if you think crashes make a race exciting. It was nothing but a crashfest. That wasn't racing."
DARF: "Oh shut up you stupid lady. If you don't like crashes, leave the sport and never come back. You know what, only come back when you make me a sandwich. Run along now."