What is the meaning of "wafer" in this extract from The Great Gatsby by F. Scott Fitzgerald, chapter 3:
The caterwauling horns had reached a crescendo and I turned away and cut across the lawn toward home. I glanced back once. A wafer of a moon was shining over Gatsby’s house, making the night fine as before and surviving the laughter and the sound of his still glowing garden.
Does it mean only "disc"?
There are many poetic devices used in this chapter. The reference to the moon is a metaphor comparing that celestial body to a wafer, or very thin piece of candy or pastry. The moon is full and round, but very unsubstantial. It will not last long, just like the music that has crescendoed and the feverish pitch of the party, which will die down as the night grows older and the guests grow more drunk and tired.
Colors are important in this chapter as well. Throughout the book-- and particularly in this chapter-- we see the importance of the color YELLOW in varying tones. There seems to be a golden glow over the entire scene, which may well be enhanced by the moonlight. The moon shines over a party scene in which Gatsby's station wagon is compared to a "brisk yellow bug." The turkeys and Jordan's arm are both gold. The cocktail music is described as yellow, as are the yellow dresses on two girls sitting at Nick's table.
The color yellow is associated with opulence-- and also with decadence. Presumably, as the wafer of the moon wanes, so too will the moral fiber of the people involved. There is much foreshadowing here of the downfall that Gatsby will soon experience.