1. a small pouch (convenient for traveling) connected by horizontal straps that are encircled around the waist, fastened by a buckle/button of some sort. suitable to contain any type of small traveling/hiking/photographing necessities
-called 'fannypack' because the bulk of the pouch rested on the (hindquarters) fanny
(see american usage... or british if you prefer).
-typically seen resting on the front/back of tourists, however there has been a spotted trend amongst the hipster
type where the fannypack is worn off to the side (a slight diversion from it's usual appearance)
2. a neo-slang term referring to an excess of stored of fat in the posterior region
1. "Timmy,we're going to disneyworld today, so put on your fannypack"
2. "Damn that dude/chick has one hell of a fannypack"