Glittering generalities are appeals based on emotionally charged concepts using broad claims. They rarely have real merit to them, it basically sounds great, but with no real reasoning behind the claim.
In Animal Farm, there are plenty of examples of it. Chapter one, has Old Majors idea of equality for all animals, that with rebellion against humans, animals will come together as "comrades" and live a life of equality. Of course, this sounds great, but how is that to be accomplished?
In chapter three-the sheep's new motto-"Four legs good, two legs bad" is definitely a glittering generality. It is not reasonable to assume that just because one walks on four legs, they are good, just as all tow legged creatures are not bad. It is meant to gain support, and the feeling of solidarity.
Chapter three also has another example in the explanation of why the pigs need the milk and apples. Squealer classifies the pigs as the brains in the takeover, and therefore in need of this sustenance. He issues his argument with the appeal(really a threat) that if they were denied this, Jones could come back and take over again. This most likely would not be the case merely because they did not get all the milk and apples.
In chapter five- the windmill debate is full of glittering generalities. The appeals to the animals comfort-heated stalls and less work, are a blanket promise. The windmill cannot ensure the animals security in the future.