After an idea or ideal is shot down; essentially when somebody's 'bubble is burst'. The creators are well aware that burble is also a synonymn for 'bubbling', 'babbling', or 'gurgling', but feel that, as so many words have multiple definitions, 'burble' is strong enough to uphold a new meaning.
"After all, when someone becomes disillusioned, as in so many works of literature in the modernism fad, their dreams become burbles."
(n) Proper word for a very gooey resonating fart. Usually this can only be perpetrated by someone whith a very craggy behind. Or someone who is sitting in something that is squishy and pliable like a bean bag. The sound's hilarity is only matched by the odor which usually smells like vomit.
Despite other harsh definitions, in the battle game of Dagorhir, within the Empire of Mirkwood, Burble is known to be a very sweet lady. During a tournament for assassins at Dagorhir's yearly gathering Ragnarok, all of the Mirkwood fighters set out as an envoy for the young woman, to protect her from a group of would-be killers, who, sadly, didn't even make it past Mordor. And so, Burble became immortal, even revered, as the entirety of the Mirkwoodian Family stood to protect one of their own.