Is a fest of multiple penises in an anus. It could be multiple penises in a number of anuses (i.e in a gang bang, where every one is doing anal and there is say two people to each anus). Anal fest is an number of penises festering around an anal, like a fly.
Anal fest is similar to anal invader but is based on having more than one anal invader.
Man! there are so many people going in and out, fucking that arse, it's an analfest.